ACCURACY AND RELIABILITY IN SEX
DETERMINATION USING THE OS COXA: A
COMPARISON OF METRIC VS. PHENICE METHOD
A Thesis
Presented to
The Faculty of the Department
of Anthropology
The University of Houston
In Partial Fulfillment
Of the Requirements for the Degree of
Master of Arts
By
Zuwena Salim
Dec, 2012
i
ACCURACY AND RELIABILITY IN SEX DETERMINATION USING THE OS
COXA: A COMPARISON OF METRIC VS. PHENICE METHOD
________________________
Zuwena Salim
APPROVED:
_________________________
Rebecca Storey, Ph.D.
Committee Chair
_________________________
Janis F. Hutchinson, Ph.D.
_________________________
Susan McIntosh, Ph.D.
Department of Anthropology
Rice University
_________________________
John W. Roberts, Ph.D.
Dean, College of Liberal Arts and Social Sciences
Department of English
ii
ACCURACY AND RELIABILITY IN SEX DETERMINATION USING
THE OS COXA: A COMPARISON OF METRIC VS. PHENICE
METHOD
An Abstract of a Thesis
Presented to
The Faculty of the Department
of Anthropology
The University of Houston
In Partial Fulfillment
Of the requirements for the Degree of
Master of Arts
By
Zuwena Salim
Dec, 2012
iii
ABSTRACT
Determination of biological sex is one of the most important determinations to be
made from undocumented human remains and is an essential first step in the
development of the biological profile in forensics and bioarchaeology. The chances of
attaining high levels of accuracy & reliability regarding sex identification are related to
the skeletal components analyzed and the ability of techniques utilized to analyze shape
and size differences among the sexes. Current opinion regards the ossa coxae or hip bone
as the most reliable sex indicator because it is the most dimorphic bone, particularly in
adult individuals. The aim of this study was to compare the Phenice method & metric
measurements of the os coxa to determine the most accurate and reliable method to
determine sex. Metric measurements used were the os coxa height, pubis length, ischium
length, iliac breadth, and the greater sciatic notch width. 101 individuals of known sex
from the Maxwell Museum collection were used in this study. Sex was correctly
estimated in 93.1 % of all individuals for both methods with a higher accuracy estimated
in females than males. The Phenice method incorrectly estimated 7 males and no females.
The metric method incorrectly assessed 2 females and 5 males. An intra-observer error
test completed on a random sample proved the Phenice method to be more reliable and
accurate on a repeatable basis. Previous experience in human osteological analysis was
shown to have no effect on accuracy in this test using the Phenice method, confirming
Phenice’s assertion that the technique does not require extensive experience to yield
accurate results.
iv
TABLE OF CONTENTS
PAGE
Abstract…………………………………………………………………………
iv
List of Tables…………………………………………………………………….
vii
List of Figures……………………………………………………………………
viii
Dedication……………………………………………………………………….
xi
CHAPTER
I.
Introduction………………………………………………………………
1
The Problem……………………………………………………................ 1
II.
III.
Hypothesis……………………………………………………………….
3
Literature Review…….………………………………………………….
5
Forensic Anthropology….……………………………………….............
5
Legal Significance……………………………………………………….
5
Sex Estimation…………………………………………………………..
6
Metric Methods of Sex Estimation………………………………… …..
15
Phenice Method of Sex Estimation………………………………………
16
Materials & Methods…………………………………............................
20
Source and Demography of Material………………………………. …..
20
v
Metric Measurements……………………………………………….……
21
Phenice Visual Measurements………….…………………...............…… 24
IV.
Observer Error Results…………………………………………………… 33
Intra-observer Error……………………………………………………… 33
V.
VI.
Method Results………………………………………………………….
37
Metric Measurement Method Results……………………………………
37
Phenice Method Results……………………………………………. …..
53
Discussion……………………………………………………………….
75
Reliability………………………………………………………………… 75
Accuracy…………………………………………………………………. 76
VII.
Conclusion……………………………………………………………….
86
Limitations…………………………………………………………. ……
87
Implications………………………………………………………………
88
References………………………………………………………………..
90
Appendices
A.
Data: Skeleton Population ………………………………………………
96
B.
Data: Phenice Method Results Table……………………………………
101
C.
Data: Metric Measurement Results Table………………………….........
108
vi
LIST OF TABLES
TABLE
PAGE
1.
Original data for Phenice method results…………………………………. 34
2.
Round 2 intra-observer results for Phenice method results………………. 35
3.
Group statistics for metric measurements………………………………… 37
4.
Classification results for metric measurement…………………………… 38
5.
Casewise statistics for metric measurements…………………………….
38
6.
Misclassified individuals for metric method……………………………..
44
7.
Extreme Values for metric measurements……………………………….. 50
8.
Classification results for Phenice method………………………………..
9.
Misclassified individuals for Phenice method…………………………… 54
10.
Casewise statistics for Phenice method………………………………….. 62
11.
Descriptive statistics for time……………………………………………… 74
vii
54
LIST OF FIGURES
FIGURE
PAGE
1.
Female and male Ossa coxae comparison………………………………
9
2.
Sex estimation markers of the skull……………………………………
10
3.
Long bones of the arm and leg…………………………………………
11
4.
Key differences between male and female ossa coxae…………………
12
5.
Male and female os coxa………………………………………………
13
6.
Female and male pubis bone…………………………………………..
18
7.
Os coxa landmark measurements……………………………………..
22
8.
Greater sciatic notch width……………………………………………
24
9.
Ventral arc……………………………………………………………..
26
10.
Subpubic concavity……………………………………………………
27
11.
Ischiopubic Ramus………………………………………………………
28
12.
Ventral arc orientation for scoring………………………………………
29
13.
Ventral arc scores from 1 to 5…………………………………………
29
14.
Subpubic concavity orientation for scoring……………………………
30
15.
Subpubic concavity scores from 1 to 5………………………………..
30
16.
Ischiopubic Ramus ridge orientation for scoring………………………
31
17.
Ischiopubic Ramus ridge scores from 1 to 5………………………….
32
18.
Box plot for pubis length………………………………………………
46
19.
Box plot for Ischia length………………………………………………
47
viii
20.
Box plot for greater sciatic notch…………………………………….
48
21.
Box plot for os coxa height…………………………………………….
49
22.
Box plot for iliac breadth………………………………………………
50
23.
Os coxa No. 20…………………………………………………………
55
24.
Os coxa No. 20; v. arc, Subp. concavity & Ischiopubic Ramus ridge…
55
25.
Os coxa No. 43…………………………………………………………
56
26.
Os coxa No. 43; v. arc, Subp. concavity & Ischiopubic Ramus ridge….
56
27.
Os coxa No. 65…………………………………………………………..
57
28.
Os coxa No. 65; v. arc, Sub. concavity & Ischiopubic Ramus ridge…….
57
29.
Os coxa No. 84…………………………………………………………..
58
30.
Os coxa No. 84; v. arc, Subp. concavity & Ischiopubic Ramus ridge…… 58
31.
Os coxa No. 100………………………………………………………….. 59
32.
Os coxa No. 100; v. arc, Subp. concavity & Ischiopubic Ramus ridge….. 59
33.
Os coxa No.162…………………………………………………………… 60
34.
Os coxa No.162; v. arc, Subp. concavity & Ischiopubic Ramus ridge…… 60
35.
Os coxa No. 189…………………………………………………………… 61
36.
Os coxa No. 189; v. arc, Subp.concavity & Ischiopubic Ramus ridge……. 61
37.
Os coxa No. 21…………………………………………………………….. 78
38.
Os coxa No. 21 scored using Phenice landmarks as all 1’s……………….. 78
39.
Os coxa No. 86…………………………………………………………….. 79
40.
Os coxa No. 86 scored using Phenice landmarks as all 1’s……………….. 79
41.
Os coxa No.158……………………………………………………………. 80
42.
Os coxa No.158 scored using Phenice landmarks as all 1’s……………… 80
ix
43.
Os coxa No.173…………………………………………………………… 81
44.
Os coxa No.173 scored using Phenice landmarks as all 1’s……………… 81
45.
Os coxa No. 182…………………………………………………………… 82
46.
Os coxa No.182 scored using Phenice landmarks as all 1’s………………. 82
47.
Os coxa No. 201…………………………………………………………… 83
48.
Os coxa No. 201 scored using Phenice landmarks as all 1’s……………… 83
49.
Os coxa No. 203…………………………………………………………… 84
50.
Os coxa No. 203 scored using Phenice landmarks as all 1’s……………… 84
51.
Os coxa No. 207………………………………………………………….
52.
Os coxa No.182…………………………………………………………….85
x
85
DEDICATION
To my mother, Cynthia, who continues to encourage me to learn, grow and
develop and who has been a source of encouragement and inspiration to me throughout
my life, a very special thank you for providing ‘Mom’s Taxi service’ and for nurturing
me through the months of writing. And also for the myriad of ways in which, throughout
my life, you have actively supported me in my determination to find and realize my
potential, and to make this contribution to our world.
xi
Chapter I
Introduction
Determination of biological sex is one of the most important determinations to be
made from undocumented human remains and is an essential first step in the
development of the biological profile in forensics and bioarchaeology, because sex
determination is necessary to make age, ancestry, and stature estimations, as the sexes
age differently, exhibit some degree in variation in ancestry-related morphology, and
generally differ in height (Stewart, 1979). Methods to estimate other aspects of the
complete profile heavily depend on accurate sex determination. In determining the
biological sex of an unknown skeleton, osteologists start with accuracy of 50%, the
remains will either be male or female. Therefore a random guess will be correct half of
the time. However, correct sex identification half of the time is not accurate or reliable
and tested methods must be used to accurately determine sex.
There are numerous techniques used by osteologists to estimate biological sex.
Methods vary from metric measurements of specific landmarks of sexually dimorphic
traits to visual assessments of specific landmarks located on the skeletal remains. Sexual
dimorphism refers to the differences between males and females in regards to size and or
appearance.
Various bones from the human skeleton have been used to develop methods for
sex estimation with varying degrees of success. Although other bones have been utilized,
the skeletal components often investigated for sex determination are the ossa coxae which
consist of 3 bones, the ilium, the ischium, and the pubis, the skull, and long bones which
1
consist of all of the bones in the arms and legs, except the patella, and bones of the wrist,
and ankle. Of the three skeletal elements the ossa coxae are the most widely regarded
elements to determine sex. The most reliable sexing traits are found in the ossa coxae,
due to the sexual dimorphic nature (Washburn 1948, Krogman 1962, Phenice 1969,
Buikstra and Ubelaker 1994, White 2000).
It is important that osteologists know the reliability and accuracy rates of sex
estimation so a correct identification of an unknown individual can be made. Validation
studies such as this is of importance to determine rates of accuracy and reliability in sex
determination as well as to identify methods that help us properly identify skeletal
remains. Without validation studies it is impossible to know if a method will perform in
the same or similar manner as it did on the sample it was tested on, or if the results of a
published study can be reproduced.
There are many studies that test either the metric measurement methods or the
Phenice method. However there are none that compare both methods to each other on the
same individuals. This study will not only compare accuracy and reliability, but also
show where the two methods differ in estimating sex on an individual.
2
Hypothesis
This thesis examines the rates of accuracy and reliability of sex estimation
methods for the os coxa using metric measurements and the Phenice visual method on a
modern population sample. The purpose of this research is to acquire new insight to a
previously researched problem using a modern known population and assessing the
accuracy and reliability of each technique. The assessment of the metric measurement
and Phenice visual techniques will be assessed on the same population and a comparison
to analyze the results will be completed to determine levels of accuracy & reliability. I
want to test both methods to obtain results on the method that is the most accurate and
reliable in determining sex in the quickest amount of time by an inexperienced
researcher. I expect the metric measurement and the Phenice method will both yield high
levels of accuracy & reliability in the determination of sex. However I expect accuracy
and reliability in determination of sex will be more accurate in the Phenice method and
will take significantly less time to complete the visual assessment and obtain sex
identification on a repeatable basis. Phenice states his method is much easier to determine
sex than metric measurements. I expect with a thorough reading of his research methods,
and a comparison from the picture diagram examples he provides in his research, even a
beginner researcher with minimal previous experience can yield accurate results. I also
predict that because females are under selection for having a wider pelvis that they will
be estimated more accurately than males for both the metric as well as the Phenice
method.
A relationship between biological sex and sex determination using these methods
will indicate the landmarks that display sexual dimorphism. High rates of both accuracy
3
and reliability will indicate which method should be used in forensic cases, since it is
necessary to use the methods that provide not only accurate but reliable sex estimations.
When creating a biological profile the quickest and easiest and most reliable method of
sex determination will allow anthropologists to accurately determine sex and move on to
the next important piece of the puzzle that will allow identification of the skeletal
remains. If these hypotheses are accepted, future beginner inexperienced as well as
experienced forensic anthropology researchers can use the Phenice method of sex
identification with greater confidence.
4
Chapter II
Literature Review
Forensic anthropology is the identification of skeletal remains in medicolegal
death investigations. The medicolegal death investigation system is responsible for
conducting death investigations and certifying the cause and manner of unnatural and
unexplained deaths. Unnatural and unexplained deaths include homicides, suicides,
unintentional injuries, drug-related deaths, and other deaths that are sudden or
unexpected. Approximately 20% of the 2.4 million deaths in the US each year are
investigated by medical examiners and coroners, accounting for approximately 450,000
medicolegal death investigations annually (Hanzlick, 2003).
In order to understand the importance of forensic anthropology, it is necessary to
first define it. Forensic anthropology is a specialty discipline combining biological
anthropology and archaeology. Biological, or physical, anthropology is the study of
human evolution and human variation with emphasis on skeletal biology. Archaeology is
the study of past cultures based on their material remains. Both subfields are part of
anthropology, which also includes the subfields of cultural anthropology and linguistics.
While physical anthropology is the study of normal variation in the skeleton, forensic
anthropology explores how external factors affect the skeleton, emphasizing the
individual variation across populations (Isçan 1988).
The American Board of Forensic Anthropology defines forensic anthropology as
the application of the science of physical anthropology to the legal process. In forensic
anthropology, archaeology and biological anthropology converge in the medicolegal
5
setting. The identification of skeletal human remains is important to this legal process.
Forensic anthropologists use archaeological techniques to recover human remains and
other evidence from the field in a controlled manner, while the biological
anthropologist’s detailed knowledge of human skeleton variation leads to the
identification of the remains. The primary goal of forensic anthropology is the
identification of individuals who are no longer recognizable, for example from severe
burning, decomposition, or skeletonization (Rhine, 1998). Forensic anthropologists apply
standard scientific techniques developed for the purpose of physical anthropology to
identify human remains, and to assist in the detection of crime. Forensic anthropologists
frequently work in conjunction with homicide investigators to identify remains, discover
evidence of foul play, and/or the postmortem interval. In addition to assisting in locating
and recovering suspicious remains, forensic anthropologists work to estimate the age,
sex, ancestry, stature, and any unique features of skeleton remains. When skeletonized
remains are discovered, the forensic anthropologist must first establish if the bones are
human. If the remains are human, sex, race/ethnicity, age, stature, weight, and any
pathology present must be established in order to make an identification of the remains,
and determine manner and cause of death. Once the Forensic Anthropologist establishes
identity or a possible identity, he or she must also make a report and possibly testify in
court. And although forensic anthropologist typically do not have the legal authority to
declare the official cause of death, their opinions are taken into consideration by the
medical examiner and they may also have to testify in court as an expert witness.
The foundation of forensic anthropology rests on “documented” skeletal
collections, which provide a crucial repository of information from which experts can
6
rely upon to make accurate determinations about the skeletal remains. A “documented”
skeletal collection is one in which the demographics (e.g., ancestry, sex, age, height) of
each individual are supported by known facts about the decedent at the time of his/her
death (Vitek, 2005). Substantial collections of skeletons where sex and other data, such as
age at death, are known for individual skeletons are few in numbers (Mays, 2010).
When a person’s death is set within a forensic context, it is the forensic
anthropologist’s responsibility to interpret the “evidence” recorded in the bones to
determine identity and the circumstance of his or her death. To accomplish this, forensic
anthropologists begin by establishing a biological profile of the skeleton. The biological
profile consists of the sex, age, ancestry, and stature, as well as any skeletal anomalies or
pathologies that make an individual unique (Steadman, 2009).
Human skeletal remains often reach the forensic anthropologist without any
documentation about their individual age, sex, stature, or ancestral identity. The bulk of
the literature of human osteology is composed of thousands of books and articles
describing the development of methods to allow accurate and precise identification of
individual’s traits in skeletal remains. This research continues today, even after a century
of intensive study. In forensic osteology, these individuals’ biological attributes are
important in narrowing the field of investigation to certain subsets of people and in
establishing the identity of the remains (White and Falcons, 2005).
Determination of sex is an essential first step in the development of the biological
profile in human osteology. Accurate sex determination is of vital importance in
forensics, because sex determination is necessary to make age, ancestry, and stature
estimations, as the sexes age differently, exhibit some degree in variation in ancestry7
related morphology, and generally differ in height (Stewart, 1979). Methods to estimate
other aspects of the complete profile depend on accurate sex determination.
As stated in the previous chapter various bones from the human skeleton have
been used to develop methods for sex estimation with varying degrees of success.
Although other bones have been utilized, the skeletal components often investigated for
sex determination are the ossa coxae which consist of 3 bones, the Ilium, the Ischia, and
the pubis, the skull, and long bones which consist of all of the bones in the arms and legs,
except the patella, and bones of the wrist, and ankle. Sex identification of adult human
skeletal remains is more reliable if the complete skeleton is available for analysis.
However, more often than not the complete skeleton is not available. In a sample of 750
intact skeletons, Krogman (1973) reported numbers very close to 100% accuracy of sex
identification. In the sample, he achieved 80% accuracy when using the long bones and
around 90% when only the skull was used for sex identification, however using only the
pelvis he yielded an accuracy of 95% in determining sex.
Frequently, sex determination is not straight forward, as there is considerable
overlap between the sexes. Normal human variation can produce small males and robust
females, therefore anthropologists must rely on specific skeletal traits that are known to
be sexually dimorphic (White and Falcons, 2005).
Sexual dimorphism is slight in
anatomically modern human populations, however primary differences can be observed
in skeletal elements (White and Falcons, 2005). The ossa coxae are considered the most
sexually dimorphic skeletal elements in humans because the female pelvis must
accommodate the relatively large head of an infant during childbirth. Thus, as seen in
figure 1, the female pelvis is typically wider in every dimension than the male pelvis
8
(Steadman, 2009). In general the female pelvis is broader than the male. A narrow pelvis
is more efficient for locomotion, but in females a broader pelvis is dictated by the fact
that it forms the birth canal. Women with narrow pelvises are more likely to experience
potentially life threatening problems during childbirth; thus most researchers agree that
the principal reason for the evolution of pelvic sexual dimorphism in humans and other
primates is natural selection in relation to childbirth in females (Tague, 1995).
Figure 1 Female and male ossa coxae comparison
(Adapted from The Crime Lab: Staples High School Forensics website: Images from http://www.clipart.com, and
adapted by Mr. Lazaroff)
The skull is somewhat less reliable for use in determining sex, ranging between
80 and 90 percent accuracy (Williams and Rogers, 2006). Males are generally larger and
more robust than females, and this is the same in regards to the skull, although for some
individuals this is not the case, females can also be large and robust as well as males can
9
be gracile & dainty. Although sexual dimorphism in the human skull is not as
pronounced as in many other primates, there are sex indicators, such as the brow ridges,
mastoid processes, and the nuchal crest shown in figure 2 which are more developed in
the male (Mays, 2010).
Figure 2 Sex estimation markers of the skull (female (L) & male (R)): 1 eye brow ridge 2 mastoid process 3 nuchal
crest
(Scanned from http://ossamenta.dreamwidth.org)
The long bones, which are pictured in figure 3, also can be useful in sex
estimation studies. The long bones are generally longer and more robust in males as
opposed to females, and muscle attachments tend to be larger in males than females.
However, because of the variation in the activities performed by each sex, the possibility
that some females may develop larger muscle attachments than males is highly possible.
Also, because of variations in height within populations long bones may not always be
10
the most reliable bones for use in sex identification unless it is in conjunction with other
bones .
Figure 3 Long bones of arm: Humerus, Radius, Ulna & long bones of the leg: Femur, Tibia, and Fibula
(Arm bones adapted from http://thesebonesofmine.wordpress.com/category/humerus; Leg bones adapted from
http://www.adam.com/healthsolutions)
Current opinion regards the ossa coxae also as the most reliable sex indicator
because it is the most dimorphic bone in the human body, particularly in adults and is the
first bone assessed in sex determination because it is the skeletal element most affected
by reproduction and parturition which refers to the process of labor and delivery
associated with child birth (Byers, 2005) (White and Falcons, 2005).
11
Figure 4 key differences between male (l) and female(r) ossa coxae
(Adapted from Bluegrass Community and Technical College's BIO 137 virtual lab http://www.bluegrass.kctcs.edu/)
The ossa coxae is the most accurate area used to determine sex and methods
utilizing these elements tend to make successful predictions in 90-95 percent of
individuals (Iscan, 2005). In humans, the pelvis is on average larger in females than
males as seen in figure 4 & 5 (Tague, 1992). In both sexes, the pelvis functions in
locomotion, posture, visceral support and adaptation to climate (Abitbol, 1988, Lovejoy
1988, Ruff 1991). Sexual dimorphism in the pelvis area is mainly due to the changes that
occur during adolescence to meet the requirements of childbirth in females (Iscan, 2005).
The female pelvis grows more in width than in height during adolescence, while the
12
growth of the male pelvis maintains the morphological characteristics of both sexes
before adolescence (White and Falcons, 2005). Therefore, a wide pelvic inlet, wide sub
pubic concavity, and a wide greater sciatic notch are all characteristic of the female
pelvis, while the opposite characteristics are found in the male pelvis among adults as
seen in the figure below. Because these changes occur after adolescence it is usually not
as easy to distinguish sex in juvenile populations.
Figure 5 Male os coxa (l) & female os coxa (r)
(Adapted from Smithsonian National Museum of Natural History:
http://anthropology.si.edu/writteninbone/male_female)
13
Sex determination using the ossa coxae can be accomplished through
morphological characteristics which refer to the form and structure or metric analysis of
linear measurements which are measured with a caliper and or osteometric board (Rogers
& Saunders, 1994). Traditional methods used to determine sex on the ossa coxae or its
parts are based on the following tendencies: the sacra and ossa coxae of females are
smaller and less robust than those of males. Female pelvic inlets are relatively wider than
males. The greater sciatic notches on female ossa coxae are relatively wider than those on
male bones. Females have relatively longer pubic portions of the os coxa, including the
superior pubic ramus, than males. The sub-pubic angle formed between the lower edges
of the two inferior pubic rami, is larger in females than in males. The preauricular sulcus
is present more often in females than in males. A corollary is that the auricular surface is
more elevated from the female Ilium than from the male Ilium, even though sexual
dimorphism in the auricular surface itself is insufficient for accurate sexing (Ali and
MacLughlin, 1991). Usually an osteologist would use more than one element to
determine sex for higher rates of accuracy.
Regions of analysis are not the only factors for consideration when attempting to
determine sex in an individual skeleton. Methods are also divided by the types of data
used to make determinations. There are two main approaches to sex identification, the
first is based on a visual assessment of the shape or relative proportions of sexually
dimorphic features of the bone. The second is a metric measurement method, which
MacLaughlin (1990) states offer several advantages over the visual approach in that 1. It
is inherently more objective, 2. Replicability is high, 3. It is less dependent on previous
observer experience, and 4. It is more readily amenable to statistical analysis and thus
14
facilitates between sample and between study comparisons. However, it does depend on
readily identifiable and unambiguous skeletal landmarks. And it is well known that
normal human variation can produce small males as well as small females, robust males
as well as robust females and many variations in between.
Metric methods rely on the general observations that males of a given population
tend to be larger than females. The metric method utilizes individual measurements or
combinations of measurements to separate the sexes and make determination based on
that. Morphological methods rely on either the presence or absence of certain traits, or the
degree of expression for a particular trait. The presence or absence of the ventral arc or
the width of the greater sciatic notch are commonly used to estimate sex and are two of
the various landmarks that were used in this research.
Metric Methods of Sex Estimation
Researchers in favor of metric methods profess they are more easily repeatable
than morphological methods because they rely on standardized osteometric elements or
landmarks. In addition, metric methods are more objective than non-metric methods,
because osteometric landmarks tend to be easier to find on a consistent basis and the
assessment is not based on judgment against a specific scale .
A variety of metric techniques have been developed to express these relationships.
Washburn's measurement of the relative proportion of the pubis part of the ossa coxae is
the most famous and effective of these. Washburn (1948) measured the length of the
pubis relative to the length of the ischium via an index that differentiated between male
and female ossa coxae. Rogers and Saunders (1994) provide a review of metric and
morphological traits used to sex the pelvis, and Bruzek (2002) provides a more current
15
assessment (White, 2005). For example Steyn and Iscan’s metric analysis on a Modern
Greek population showed that most measurements were “highly repeatable” and when all
variables are present, the average accuracy is 95.4% (Iscan, 2005).
Traditional metric analysis of the human skeleton have been claimed by many to
be more repeatable and a more case-inclusive method of determining sex, which can be
performed by less experienced practitioners and can also expose significant areas of
variation that may not be readily recognizable via visual observation (Giles, 1963).
However, those in favor of visual methods say that many traditional
measurements are difficult to repeat because they are based on landmarks that are
difficult to locate. Problematic examples include pubis and ischium lengths which are
measured from an often indeterminate point in the acetabulum (A. Schultz, 1930). Sex is
generally determined in adult skeletons from a simple visual inspection of the bones.
Although some methods have been devised based on measurements of the skull (Giles
and Elliot 1963) and pelvis (Schulter-Ellis et al. 1983, 1985; Albanese, 2003)
measurement methods do not generally offer improvements in reliability over visual
inspection (Mays, 2010).
Phenice Method of Sex Estimation
In 1969 T.W Phenice published a new method for sexing the pelvis. “A Newly
Developed Visual Method of Sexing the Os Pubis," and is by many described as the most
accurate method yet known for determining sex of an individual from the skeleton. Until
the publication of the Phenice paper, osteologist's success at using traditional visual
methods of sexing the pelvis depended, in large part, on experience, decisions were more
or less subjective. The application of metric criteria was difficult because much of the
16
material was too fragmentary for reliable measurement, and even the simplest techniques
were time consuming. Phenice's method changed the situation, allowing more accurate,
quicker sexing on any pelvis with an intact pubic region (White, 2005).
Phenice came up with three aspects of the pelvis he felt were useful to estimate
sex of human skeletal remains, the ventral arc, the subpubic concavity, and the medial
aspect of the ischiopubic ramus (Phenice, 1969). The ventral arc refers to a slight
elevated ridge of the bone which extends from the pubic crest and arcs inferiorly across
the ventral surface to the lateral most extension of the subpubic concavity. Phenice
reported that the ventral arc has only been detected in females. He suggests that males
may present a similar ridge, it does not match the above definition when the bone is
oriented correctly (Phenice, 1969). The subpubic concavity refers to the lateral recurve in
the dorsal ischiopubic ramus a short distance below the lower margin of the pubic
symphysis. Phenice describes this as a female characteristic, noting that some males
display a "slight hint" of the trait (Phenice, 1969). Phenice also noted that in males, the
medial aspect of the ischiopubic ramus displays a broad, flat surface. In contrast, in
females, this area more frequently presents a ridge.
To examine the usefulness of the three traits in estimating sex, Phenice examined
pelvic bones of 275 individuals of known sex from the Terry Collection. Of the 95
females examined, 43 were of European ancestry and 52 of African ancestry. Of the 180
males, 160 were of European ancestry and 20 of African ancestry. Using the three criteria
above, Phenice was able to estimate the sex with an accuracy of 96%. His procedure was
more accurate for females than for males and slightly more accurate for individuals of
European ancestry than for those of African ancestry. He recommended using all three of
17
the criteria noting when there is some ambiguity concerning one, or rarely two of the
criteria, there is almost always one of the criteria which is obviously indicative of male or
female (Phenice, 1969). Although Phenice identified the three traits of the anterior pubis
that accurately determine sex as seen in figure 6, Buikstra & Ubelaker (1994) devised a
scoring system for these three traits: 1 = female, 2 = probable female 3 =ambiguous, 4=
probable male and 5 = male (Buikstra & Ubelaker, 1994).
A key attraction of the Phenice method is that he claims levels of high accuracy
even with inexperienced researchers. According to Phenice, the method he describes is
simple and objective enough to allow even beginning researchers to sex hip bones
accurately (Phenice, 1969).
Figure 6 Female & male pubis bone (Scanned from Sutherland and Suchey 1991:502)
18
In 1990, McLaughlin and Bruce tested the Phenice technique for accuracy of sex
identification on skeletal series from London, Leiden, and Scotland. They were unable to
confirm the accuracy obtained by Phenice and others, achieving success in only 83% of
the English, 68% of the Dutch, and 59% of the Scottish. They found the subpubic
concavity to be the single most reliable indicator. Sutherland and Suchey (1991) tested
aspects of the Phenice technique using 1284 pubic bones from the Los Angeles County
Coroner’s Collection. The pubic bones had been removed from cadavers, therefore not all
3 of the features could be tested. However, Sutherland and Suchey (1991) reported that
they achieved 96% sexing accuracy using the ventral arc alone.
Ubelaker (Ubelaker and Volk, 2002) notes that experience plays a role in
accuracy of results from the use of the techniques. I will test if experience plays a role in
accuracy of results from the use of the metric measurements vs. the Phenice method.
Philip Walker found that the visual observation of the greater sciatic notch produced
about the same proportion of correct sex assessment as using metric methods (Walker,
2005). This validation study will determine rates of accuracy and reliability in sex
determination as well as identify methods that help us properly identify skeletal remains.
19
Chapter III
Materials &Methods
Materials
The Maxwell Museum of Anthropology, part of the University of New Mexico,
was established in 1984. The Maxwell Museum’s Documented Skeletal Collection has
grown to include 255 individuals (as of September 2003) encompassing both sexes, all
ages, and many population groups. The skeletal remains are obtained by donation, either
by the individual before death, by the family of a deceased loved one, or by the Office of
the Medical Investigator when the next of kin cannot be located. Information on the sex,
age, population affinity, and cause of death is available for the majority of these
individuals, so that students and visiting researchers can develop and test new techniques
and theories. The importance of the Documented Collection cannot be overstated because
they are few in numbers. No other institution in the American West has as large a
collection of human skeletal remains with such extensive demographic data. In addition,
the Maxwell Museum’s collection consists entirely of individuals who passed away
within the last 30 years.
A sample of 101 intact os coxa of documented sex, age, and population of similar
or same ancestry from the University of New Mexico housed at the Maxwell Museum
was used for this research. The right os coxa was used unless there was damage. If this
was the case the left was used. All skeletal samples used in this research consisted of
adults because age has an important impact on sex determination with juveniles being
much harder to determine sex. There have been many attempts but not much success for
20
accurate and reliable methods on juvenile or sub adult populations. Sex estimation for
only adults is the focus of this study.
Any os coxa that was broken or contained pathologies or anomalies was not used.
The sample consist of 66 males (65%), and 35 females (35%) ranging in age from 19101. Ancestry of the population consists of 90 Whites (89%) and 11 (11%) of unknown
ancestry.
All measurements were taken using a digital sliding caliper and all measurements
were recorded to the nearest millimeter and collected using techniques outlined in the
UTK publication Data Collection Procedures for Forensic Skeletal Material (MooreJansen et al. 1994). The amount of time to obtain measurements was also recorded with a
stop watch. Pictures of all os coxa used in research were also taken. Estimations for sex
were made for each individual without prior knowledge of biological sex for the Phenice
method and discriminate function analysis was used to estimate sex for the metric
measurements.
Methods
Measurements
Measurements used in this study were selected on the basis of 3 factors. 1)
expected dimorphism, 2) easily identifiable landmarks (for repeatability and consistency)
and 3) portions of the pelvis that are more likely to remain intact. All dimensions for
metric measurements were taken to the nearest millimeter with a sliding digital caliper.
Data was subjected to statistical analysis using SPSS programs.
21
Metric measurements taken included, the height of os coxa, the iliac breadth of os
coxa, the pubis length, the ischium length, and the width of the greater sciatic notch
which are shown in figure 7. SPSS, discriminate function analysis was used to determine
sex for the metric measurement method which compared the metric method to actual
documented sex to determine accuracy. The time it took to obtain each measurement was
also noted to later compare with the Phenice visual method times.
Measurement Definitions for Metric Measurements
Figure 7 Os coxa landmark measurements
(Adapted from: Buikstra and Ubelaker, 1994; Moore-Jansen et al., 1994)
22
•
Os Coxa: Height: Distance from the most superior point on the iliac crest to the
most inferior point on the ischial tuberosity. Instrument: spreading caliper or osteometric
board( A)
•
Os Coxa: Iliac Breadth: Distance from the anterior-superior iliac spine to the
posterior-superior iliac spine. Instrument: spreading caliper (B)
•
Os Coxa: Pubis Length: Distance from the point in the acetabulum where the
three elements of the os coxa meet to the upper end of the pubic symphysis. Instrument:
sliding caliper. Comment: the measuring point in the acetabulum may be identified in the
adult by (1) an irregularity which is frequently visible, both on the acetabular and pelvic
surfaces; (2) a change in thickness which may be seen by holding the bone up to a light;
(3) a notch often present in the border of the articular surface in the acetabulum. In
measuring the pubis, care should be taken to hold the caliper parallel to the long axis of
the bone (C)
•
Os Coxa: Ischium length: Distance from the point in the acetabulum where the
three elements meet to the deepest point on the ischial tuberosity. Instrument: sliding
caliper. Comment: Ischia length should be measured approximately perpendicular to
pubis length (D)
 Width of Greater Sciatic Notch: Distance from inner notch to outer notch just
inferior to the posterior inferior iliac spine.
23
Figure 8 Greater sciatic notch width
(Adapted from Biology 121 HACC with Professor John Sword for lab practical 1: quizlet.com)
The landmarks to be recorded for the subpubic region of the os coxa using the
Phenice method include the ventral arc, the subpubic concavity, and the Ischiopubic
ramus ridge. These landmarks are illustrated in figures 9, 10, & 11. Females present
positive expression of these attributes. According to Phenice (1969), the ventral arc is the
most reliable indicator; the ischiopubic ramus ridge the least. Estimation of sex was made
for each individual without prior knowledge of biological sex. Each observation was
timed and recorded with a stop watch, also pictures were taken of each landmark.
Phenice’s method was then compared to the actual documented sex to determine
accuracy. A number between one and five was assigned to each of the visual traits for
individual, corresponding to sex as follows;
24
1= female- There is little doubt that the structures represent a female
2= probable female- The structures are more likely to be female than male
3= ambiguous- Sexually diagnostic features are ambiguous
4= probable male- The structures are more likely to be male than female
5= male- There is little doubt that the structures represent a male
No weight was given to any one feature and at least two out of three characters
were required to be in agreement of sex before sex was assigned. For an os coxa to be
scored as a female, a minimum of two scores of “1” or “2” was required. For an os coxa
to be scored as male, a minimum of two scores of “4” or “5” was required. An exception
was made if the os coxa was scored as a “3” ambiguous for 2 traits. If 2 traits were scored
as a “3”,the sex was chosen based on 3rd feature that was not ambiguous.
25
Visual Method Landmark Definitions
Figure 9 Ventral Arc: A (female), B (male)
(Adapted from Figure 1, Phenice 1969:299.)
Ventral Arc: Present in females. As seen in figure 9, it is a ridge of bone on the anterior
aspect of the pubis and the curve “cuts off” the infero-medial corner of the bone. If male
bones exhibit a ridge, it does not have the same curve, angling instead infero-medially to
conform with the edge of the bone.
26
Figure 10 Subpubic Concavity: C( female), D (male)
(Adapted from Figure 1, Phenice 1969:299.)
Subpubic Concavity: Present in females when viewed from an anterior aspect. As seen in
figure 10, the inferior border of the Ischiopubic Ramus is concave when this trait is
present, as opposed to the straight or convex morphology seen in males.
27
Figure 11 Ischiopubic Ramus ridge E (female), F (male)
(Adapted from Figure 1, Phenice 1969:299.)
Ischiopubic Ramus: As seen in figure 11, the medial surface of the Ischiopubic Ramus
immediately below the symphysis forms a narrow, crest like ridge in females. Thin in
females when viewed from the medial aspect; noticeably thicker in males.
28
For assessment of the ventral arc, the ventral surface of the pubic bone should be
perpendicular to the viewer and the superior pubic ramus should be aligned horizontally
or straight as seen in figures 12 & 13. For this trait, the area lateral to the symphyseal
face should be assessed.
Figure 12 Ventral arc orientation for scoring
(Adapted from http://nonmetricpelvissexing.weebly.com/ventral-arc.html)
Trait Scoring
Figure 13 Ventral arc from left to right: score 1 (f) to 5 (m) (Adapted from
http://nonmetricpelvissexing.weebly.com/ventral-arc.html)
29
For the subpubic concavity, the dorsal surface of the pubic bone should be held
perpendicular to the scorer. The region immediately below the symphyseal face and the
entire inferior pubic ramus should be considered as seen in figures 14 & 15.
Figure 14 Subpubic concavity orientation for scoring
(Adapted from http://nonmetricpelvissexing.weebly.com/subpubic-contour.html)
Trait Scoring
Figure 15 Subpubic concavity from left to right: score 1 (f) to 5 (m)
(Adapted from http://nonmetricpelvissexing.weebly.com/subpubic-contour.html)
30
To assess the medial aspect of the ischio-pubic ramus, the symphyseal face should be
held perpendicular to the viewer. The superior and inferior borders of the symphyseal
face should be aligned vertically. To asses this trait the region below the inferior edge of
the symphyseal face to the approximate mid-region of the ramus should be considered as
seen in figures 16 &17.
Figure 16 Medial aspect of the Ischiopubic Ramus ridge
(Adapted from http://nonmetricpelvissexing.weebly.com/medial-aspect.html)
31
Trait Scoring
Figure 17 Ischiopubic Ramus ridge from left to right: 1 (f) to 5 (m)
(Adapted from http://nonmetricpelvissexing.weebly.com/medial-aspect.html)
32
Chapter IV
Intra-Observer Error
Observer error analysis is important in determining the reliability of methods for
data collection in scientific research. In order for a method to be reliable, its results must
be repeatable. If the results of a method cannot be replicated, it will not be useful for the
purpose of scientific research. Reliability is tested here with an intra-observer error study.
In order to test for intra-observer repeatability of the metric & Phenice measurements, os
coxa of 15 individuals were measured a second time after the completion of the original
data set.
Phenice Method
The Phenice method was assessed for sex identification in less than 42 seconds
per os coxa on round two with an average of 21 sec from start to finish of the three
landmarks. Two of the os coxa were assessed incorrectly for sex out of the 15, these same
two were assessed incorrectly for sex the first round as well (os coxa 84 & 100) with
identical scores for each of the landmarks.
33
Table 1.Original data for Phenice Method Results of Random Sample
Os coxa
Ventral Arc
SubPConcavity Ischio R.
No.
Estimated
Ridge
Sex
Actual Sex
42
4
2
4
Male
Male
52
3
4
4
Male
Male
53
4
4
4
Male
Male
69
4
4
4
Male
Male
73
3
4
4
Male
Male
81
4
4
4
Male
Male
84 *
3
2
2
Female
Male
87
4
4
4
Male
Male
95
4
4
4
Male
Male
100*
2
2
2
Female
Male
113
4
4
5
Male
Male
137
4
4
4
Male
Male
154
4
4
4
Male
Male
157
4
4
5
Male
Male
161
4
3
4
Male
Male
34
Table 2. Round 2 of Phenice Method Results of Random Sample
Os coxa
Ventral Arc
SubPConcavity Ischio R.
No.
Estimated
Ridge
Sex
Actual Sex
42
4
2
4
Male
Male
52
4
4
4
Male
Male
53
4
4
4
Male
Male
69
4
4
4
Male
Male
73
4
4
4
Male
Male
81
4
4
4
Male
Male
84*
3
2
2
Female
Male
87
4
4
5
Male
Male
95
4
4
4
Male
Male
100*
2
2
2
Female
Male
113
4
4
5
Male
Male
137
4
4
4
Male
Male
154
4
4
4
Male
Male
157
4
4
5
Male
Male
161
4
3
4
Male
Male
*Os coxa highlighted and labeled with * incorrectly estimated for sex
35
A paired sample t-test was conducted to compare the metric measurements from
the random sample of 15 individuals. Round 1 and 2 measurements were compared to
test for intra-observer error. Standard descriptive statistics including means and standard
deviation were obtained for all metric measurements. There was not a significant
difference in the measurements for os coxa height 1 (M=228.06, SD= 12.30) and os coxa
height 2 (M= 227.53, SD=10.71) with a mean difference of .53. There was not a
significant difference in the measurements for iliac breadth 1 (M=162.52, SD=8.23), but
iliac breadth 2 (M=161.23, SD=7.52) with a mean difference of 1.29 was significant.
There was not a significant difference between the measurements for pubis length
1(M=93.16,SD=5.41) and pubis length 2 (M=94.50, SD=5.17) with a mean difference of
1.34. There was not a significant difference in the measurements for ischium length 1(
M=91.03, SD=5.56) and ischium length 2 (M=92.43, SD=5.40) with a mean difference of
1.40. There was not a significant difference for the measurements for greater sciatic notch
width 1 (M=39.86,SD=5.46) and greater sciatic notch width 2 (M= 39.70, SD=5.46) with
a mean difference of .17.
These
results suggest that there are not significant differences in the intra-
observer error test done on the random sample of 15 individuals for all measurements
except the iliac breadth, although the measurement means are only different by 1.29 mm
the conditions are; t(14)=2.716, p=.017 with the p value being less than .05 which shows
a significant difference. If conditions are less than .05, I can conclude that there is a
statistically significant difference between the two measurements. Although the original
measurements are slightly different than round 2 measurements, the metric measurement
for four of the five measurements are highly repeatable.
36
Chapter V
Method Results
In table 3 pictured below the descriptive statistics for all os coxa measurements
for males and females are illustrated. Mean values for males exceed the corresponding
female measurements for all dimensions. Significant differences were observed between
the sexes for all measurements.
Table 3 Descriptive statistics for metric measurements
Group Statistics
Valid N (listwise)
ActualSex
Male
Female
Total
Mean
Std. Deviation
Unweighted
Weighted
Os_Coxa_Height
222.3129
10.22098
66
66.000
Iliac_Breadth
160.0838
7.75759
66
66.000
Pubis_Length
91.8300
5.00449
66
66.000
Ischium_Length
88.6689
5.14204
66
66.000
GreaterSciatic
40.7868
4.42014
66
66.000
Os_Coxa_Height
200.4514
13.04893
35
35.000
Iliac_Breadth
151.9146
8.45787
35
35.000
Pubis_Length
90.4420
6.00073
35
35.000
Ischium_Length
77.4577
5.33442
35
35.000
GreaterSciatic
38.6320
5.24434
35
35.000
Os_Coxa_Height
214.7371
15.33314
101
101.000
Iliac_Breadth
157.2529
8.87145
101
101.000
Pubis_Length
91.3490
5.38171
101
101.000
Ischium_Length
84.7839
7.45712
101
101.000
GreaterSciatic
40.0401
4.80755
101
101.000
37
Metric Method Results
I ran discriminate function analysis to make sex estimations for the metric
measurements. As seen in the classification results in table 4 below, 7 individuals were
incorrectly identified for sex for an accuracy of 93.1%. Females were correctly classified
in 94.3% of cases (33/35) and the males 92.4 % were correctly classified (61/66). As seen
in the casewise statistics table 5, 93.1% of the sample was correctly identified for sex.
Table 4 Classification results
Classification Results
a
Predicted Group Membership
ActualSex
Original
Count
Male
Male
Female
61
5
66
2
33
35
92.4
7.6
100.0
5.7
94.3
100.0
Female
%
Male
Female
Total
a.93.1% of original grouped cases correctly classified
Table 5 Casewise statistics
Casewise Statistics
Discrimina
Highest Group
Case
Numbe
r
Origin
1
Actu
P(D>d
al
| G=g)
Grou
Predicte
p
d Group
1
1
al
Second Highest Group
Squared
nt Scores
Squared
P(G= Mahalanobi
P(G= Mahalanobi
d
g|
s Distance
Grou
g|
s Distance
f
D=d)
to Centroid
p
D=d)
to Centroid
Function 1
.13 1 1.000
2.236
2
.000
18.811
2.480
.226
2
.005
11.005
1.460
p
5
2
1
1
.63 1
.995
4
38
3
1
1
.90 1
.976
.015
2
.024
7.401
.863
.990
.046
2
.010
9.339
1.199
.999
1.012
2
.001
14.805
1.991
.989
.029
2
.011
9.081
1.156
.977
.010
2
.023
7.525
.886
.904
.398
2
.096
4.890
.354
.697
1.273
1
.303
2.937
-.729
.805
.850
1
.195
3.687
-.935
.996
.286
2
.004
11.403
1.520
.993
.119
2
.007
10.152
1.329
.11 1 1.000
2.522
2
.000
19.625
2.573
.997
.390
1
.003
12.014
-2.481
.911
.361
1
.089
5.023
-1.256
.920
.317
2
.080
5.195
.422
.998
.609
2
.002
13.123
1.765
.824
.772
1
.176
3.855
-.979
.777
.963
2
.223
3.462
.003
.998
.593
2
.002
13.046
1.755
.979
.006
1
.021
7.648
-1.781
3
4
1
1
.83 1
0
5
1
1
.31 1
4
6
1
1
.86 1
4
7
1
1
.92 1
1
8
1
1
.52 1
8
9
2
2
.25 1
9
10
2
2
.35 1
7
11
1
1
.59 1
3
12
1
1
.73 1
1
13
1
1
2
14
2
2
.53 1
2
15
2
2
.54 1
8
16
1
1
.57 1
4
17
1
1
1
**
.43 1
5
18
2
.38 1
0
19
1
1
.32 1
6
20
1
1
.44 1
1
21
2
2
.93 1
9
39
22
1
2
**
.36 1
.809
.833
1
.191
3.721
-.944
.974
.023
1
.026
7.239
-1.706
.753
1.059
1
.247
3.286
-.828
.571
1.742
1
.429
2.317
-.537
.999
.783
2
.001
13.887
1.869
.997
.421
2
.003
12.184
1.633
.762
1.022
1
.238
3.352
-.846
.923
.301
2
.077
5.261
.437
.918
.328
1
.082
5.147
-1.284
.998
.547
2
.002
12.827
1.724
.999
.763
2
.001
13.803
1.858
.872
.556
2
.128
4.394
.239
.20 1 1.000
1.597
2
.000
16.856
2.248
.799
.874
2
.201
3.637
.050
.967
.052
1
.033
6.828
-1.628
.990
.046
2
.010
9.338
1.199
.766
1.008
2
.234
3.378
-.019
.901
.416
2
.099
4.825
.340
.996
.267
2
.004
11.278
1.501
1
23
2
2
.88 1
0
24
2
2
.30 1
3
25
2
2
.18 1
7
26
1
1
.37 1
6
27
1
1
.51 1
7
28
2
2
.31 1
2
29
1
1
1
**
.58 1
3
30
2
.56 1
7
31
1
1
.46 1
0
32
1
1
.38 1
2
33
1
1
.45 1
6
34
1
1
6
35
1
1
.35 1
0
36
2
2
.81 1
9
37
1
1
.83 1
1
38
1
1
.31 1
5
39
1
1
.51 1
9
40
1
1
.60 1
6
40
41
1
1
.86 1
.972
.029
2
.028
7.144
.816
.999
1.542
1
.001
16.675
-3.099
.999
1.380
2
.001
16.135
2.160
.976
.012
2
.024
7.464
.875
.996
.278
2
.004
11.354
1.512
.995
.198
2
.005
10.801
1.429
.656
1.424
1
.344
2.718
-.664
.987
.009
2
.013
8.613
1.078
.731
1.142
1
.269
3.145
-.789
.966
.060
2
.034
6.744
.740
.999
1.307
2
.001
15.880
2.128
.790
.910
1
.210
3.565
-.903
.980
.003
1
.020
7.778
-1.804
.953
.133
2
.047
6.137
.620
.976
.015
2
.024
7.392
.862
.849
.663
2
.151
4.111
.170
.627
1.531
2
.373
2.574
-.253
.05 1 1.000
3.652
2
.000
22.589
2.896
.003
1
.015
8.392
-1.912
6
42
2
2
.21 1
4
43
1
1
.24 1
0
44
1
1
.91 1
3
45
1
1
.59 1
8
46
1
1
.65 1
7
47
2
2
.23 1
3
48
1
1
1
**
.92 1
6
49
2
.28 1
5
50
1
1
.80 1
6
51
1
1
.25 1
3
52
2
2
.34 1
0
53
2
2
.95 1
8
54
1
1
.71 1
5
55
1
1
.90 1
2
56
1
1
2
**
.41 1
5
57
1
.21 1
6
58
1
1
6
59
2
2
.95 1
.985
6
41
60
1
2
**
.42 1
.851
.651
1
.149
4.141
-1.050
.995
.172
1
.005
10.607
-2.272
.967
.053
2
.033
6.818
.754
.972
.028
2
.028
7.159
.819
.978
.007
2
.022
7.596
.899
.979
.004
2
.021
7.713
.920
.997
.352
1
.003
11.801
-2.450
.998
.537
2
.002
12.780
1.718
.00 1 1.000
15.418
1
.000
45.812
-5.784
.997
.378
1
.003
11.950
-2.472
.03 1 1.000
4.425
1
.000
24.457
-3.961
.990
.034
2
.010
9.162
1.170
.875
.543
2
.125
4.431
.248
.14 1 1.000
2.179
2
.000
18.646
2.461
.933
.242
2
.067
5.522
.493
.863
.599
1
.137
4.278
-1.083
.991
.054
1
.009
9.452
-2.090
.998
.620
1
.002
13.172
-2.645
.988
.018
2
.012
8.851
1.118
0
61
2
2
.67 1
8
62
1
1
.81 1
8
63
1
1
.86 1
8
64
1
1
.93 1
2
65
1
1
.94 1
8
66
2
2
.55 1
3
67
1
1
.46 1
4
68
2
2
0
69
2
2
.53 1
9
70
2
2
5
71
1
1
.85 1
3
72
1
1
.46 1
1
73
1
1
0
74
1
1
.62 1
3
75
2
2
.43 1
9
76
2
2
.81 1
6
77
2
2
.43 1
1
78
1
1
.89 1
4
42
79
1
1
.71 1
.994
.137
2
.006
10.321
1.356
.990
.042
2
.010
9.280
1.189
.994
.128
2
.006
10.239
1.343
.08 1 1.000
2.893
1
.000
20.638
-3.558
.999
1.554
2
.001
16.716
2.231
.970
.038
1
.030
7.008
-1.662
.996
.314
1
.004
11.577
-2.418
.626
1.538
2
.374
2.566
-.255
.999
.842
1
.001
14.133
-2.775
.999
.914
2
.001
14.424
1.941
.984
.001
2
.016
8.278
1.020
.619
1.564
2
.381
2.532
-.266
.547
1.836
2
.453
2.211
-.370
.829
.749
1
.171
3.905
-.991
.920
.318
2
.080
5.190
.421
.965
.065
2
.035
6.697
.731
.992
.081
1
.008
9.776
-2.142
.976
.015
1
.024
7.397
-1.735
.985
.002
1
.015
8.313
-1.898
1
80
1
1
.83 1
8
81
1
1
.72 1
0
82
2
2
9
83
1
1
.21 1
3
84
2
2
.84 1
6
85
2
2
2
**
.57 1
5
86
1
.21 1
5
87
2
2
.35 1
9
88
1
1
.33 1
9
89
1
1
.97 1
2
90
1
1
.21 1
1
91
1
1
.17 1
5
92
2
2
.38 1
7
93
1
1
.57 1
3
94
1
1
.80 1
0
95
2
2
.77 1
6
96
2
2
.90 1
3
97
2
2
.96 1
7
43
98
2
2
.86 1
.989
.028
1
.011
9.047
-2.023
.943
.190
1
.057
5.789
-1.421
.830
.743
2
.170
3.920
.123
.997
.381
2
.003
11.966
1.602
8
99
2
2
.66 1
3
100
1
1
.38 1
9
101
1
1
.53 1
7
**. Misclassified case
Misclassification for males identified in individuals 42, 47, 65, 108 & 141.
Misclassification for females occurred in individuals 132, & 186 as seen in the table 6
below. Skeletons numbers differ from the numbers shown in casewise statistics which list
them in order from number 1 to 101 as opposed to actual skeleton identification number.
Table 6 Misclassified individuals
Os coxa No.
Sex Estimation
Actual Sex
Age
Ancestry
42
Female
Male
83
White
47
Female
Male
69
White
65
Female
Male
73
White
108
Female
Male
83
No Data
132
Male
Female
69
White
141
Female
Male
30
White
186
Male
Female
101
White
44
The results show that there are significant sex differences between males and
females. However it is interesting to note the measurements of specific sections of the os
coxa, for example the pubis length and greater sciatic notch width did not yield as high
results as measurements for the bone as a whole. In other studies the greater sciatic notch
usually yields better results for sex determination. This may be due to my inexperience in
regards to measuring this particular area of the bone. This shows the importance of
having multiple measurements to asses. Of all metric measurements ischium length and
os coxa height were the most dimorphic.
Pubic length was greater in males ranging from 82.3-106.5 as opposed to females
ranging from 75.6-101 but the difference is so small that it is not an effective sex
predictor yielding a mean of 91.8 for males and 90.4 for females. However it is
interesting to note that as seen in the box plots below although the male and female
measurements are very similar, there are several outliers in the female range that fall well
below the normal range. Of the five that fell below the normal range, sample 186 (86)
was incorrectly classified as a male during the metric discriminate function analysis.
45
Figure 18 Box plot for pubis length
Ischium length differed significantly in males and females and was greater in
males ranging from 76.1-100.6 and 55.3-84.5 in females. The mean for ischium length in
males was 88.67 for males as opposed to 77.46 in females with one outlier which is
shown in the box plot below in figure 19, sample 158 (68) a female who actually had the
shortest Ischium length in the sample.
46
Figure 19 Box plot for Ischial length
Although the size, angle and shape of the greater sciatic notch are good
characteristics to distinguish the sexes, it can be difficult to actually quantify the
differences. The width of the greater sciatic notch is larger in females, but deeper in
males (S. Singh, 1978). The greater sciatic notch width was greater in males ranging from
25.80-48.12 as opposed to 31.51-48.79 in females but the difference is so small that it
may not be the most effective measurement for sex prediction with a mean of 40.79 for
males and 38.63 for females. The assessment of the greater sciatic notch may be more
agreeable to morphological methods as opposed to metric measurement comparisons. As
seen in the box plot below there were two outliers in the sample both were males,
individuals 53 (27 ) & 65 (30 ) which had significantly smaller width than all of the
males as well as some of the females.
47
Figure 20 Box plots for greater sciatic notch
The os coxa height yielded the most significant differences with males having a
greater height ranging from 197.9-244.3 and females ranging from 164.48-221.91. The
means show the significance differences in height with males averaging a height of
222.31 and females averaging a height of 200.45. There are two outliers in the sample
with significantly shorter os coxa heights, both of which are females, individuals 158 (68)
and 160 (70).
48
Figure 21 Box plots for os coxa height
The iliac breadth also differed significantly for males and females with males
having a higher breadth ranging from 140.1-174.3 and females ranging from 127.9-165.6.
The means from males was 160.08 and females were 151.91. There was one outlier in the
sample as shown below, individual 158 (68 ) which fell below the entire sample. Os coxa
158 had smaller measurements across all measurements and more than likely was a very
tiny female.
49
Figure 22 Box plots for iliac breadth
As seen table 7 below the os coxa height and ischium length were the only
measurements that yielded extreme highest and lowest measurements that fell into only
males for the highest and females for the lowest. This leads me to believe these are two of
the better measurements to use for sex identification.
Table 7 Extreme values for sample
Extreme Values
ActualSex
Os_Coxa_Height
Male
Case Number
Highest
Lowest
Value
1
67
244.32
2
51
242.97
3
88
241.49
4
34
241.02
5
37
241.02
1
60
197.85
2
18
198.99
50
Female
Highest
Lowest
Pubis_Length
Male
Highest
Lowest
Female
Highest
Lowest
Ischium_Length
Male
Highest
3
3
204.25
4
22
208.07
5
55
209.28
1
25
221.91
2
15
217.65
3
21
214.75
4
75
214.13
5
97
213.81
1
68
164.48
2
70
165.30
3
42
186.44
4
66
188.14
5
9
188.71
1
37
106.45
2
27
101.77
3
58
100.25
4
45
99.00
5
40
98.80
1
11
82.29
2
55
84.21
3
22
84.26
4
79
84.31
5
46
84.53
1
84
101.00
2
77
100.22
3
97
98.79
4
75
97.91
5
69
96.16
1
9
75.58
2
10
77.78
3
68
79.27
4
86
80.23
5
92
80.48
1
58
100.55
2
27
99.67
3
80
96.71
4
37
96.07
51
Lowest
Female
Highest
Lowest
GreaterSciatic
Male
Highest
Lowest
Female
Highest
Lowest
Iliac_Breadth
Male
Highest
5
13
95.63
1
22
76.06
2
19
77.02
3
18
77.02
4
60
78.73
5
91
80.79
1
75
84.47
2
24
84.09
3
57
83.62
4
28
83.21
5
25
83.03
1
68
55.30
2
82
70.01
3
10
70.67
4
42
72.16
5
70
73.29
1
78
48.12
2
64
47.81
3
58
47.74
4
81
47.29
5
46
46.95
1
27
25.80
2
30
30.77
3
22
31.92
4
32
31.98
5
80
33.02
1
47
48.30
2
53
47.15
3
52
46.12
4
57
46.00
5
28
45.20
1
36
31.51
2
15
31.61
3
97
31.71
4
68
32.64
5
9
32.75
1
35
174.27
52
Lowest
Female
Highest
Lowest
2
45
172.82
3
88
169.50
4
48
169.44
5
44
169.27
1
19
140.04
2
18
140.04
3
55
142.92
4
60
146.69
5
22
148.02
1
53
165.56
2
21
164.78
3
24
164.58
4
77
164.51
5
23
161.71
1
68
127.89
2
10
136.87
3
36
140.62
4
98
142.09
5
66
143.14
Phenice Method Results
Using the Phenice method, 94 of 101 individuals were correctly assessed for sex
for an overall accuracy of 93.1%. Accuracy was much greater for females (100%) than
for males (89.4%) as seen in the table 8 below. Of the 7 individuals who were judged
incorrectly, all 7 (59/66) were males incorrectly identified as females, no females were
incorrectly classified. As seen in table 9 all 7 males were of White ancestry and the ages
at death of the 7 individuals ranged from 40-87 years with a mean age of 66 years.
53
Table 8 Classification results
Classification Results
a
Predicted Group Membership
ActualSex
Original
Count
Male
Female
%
Male
Female
Male
Female
Total
59
7
66
0
35
35
89.4
10.6
100.0
.0
100.0
100.0
Table 9 Misclassified Individuals for Phenice Method
Os Coxa No.
Sex Estimation
Actual Sex
Ancestry Actual Age
20
Female
Male
White
87
43
Female
Male
White
71
65
Female
Male
White
73
84
Female
Male
White
68
100
Female
Male
White
40
162
Female
Male
White
54
189
Female
Male
White
69
54
Figure 23 Os coxa 20
Figure 24 Os coxa 20: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 2
Subpubic Concavity: 2
Ischiopubic Ramus: 3
Judged as female but actually a male
55
Figure 25 Os coxa 43
Figure 26 Os coxa 43: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 2
Subpubic Concavity: 2
Ischiopubic Ramus: 3
Judged as female but actually a male
56
Figure 27 Os coxa 65
Figure 28 Os coxa 65
Ventral Arc: 3
Subpubic Concavity: 2
Ischiopubic Ramus: 2
Judged as female but actually a male
57
Figure 29 Os coxa 84
Figure 30 Os coxa 84: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 3
Subpubic Concavity: 2
Ischiopubic Ramus: 2
Judged as female but actually a male
58
Figure 31 Os coxa 100
Figure 32 Os coxa 100: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 2
Subpubic Concavity: 2
Ischiopubic Ramus: 2
Judged as female but actually a male
59
Figure 33 Os coxa 162
Figure 34 Os coxa 162: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 2
Subpubic Concavity: 2
Ischiopubic Ramus: 3
Judged as female but actually a male
60
Figure 35 Os coxa 189
Figure 36 Os coxa 189: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
Ventral Arc: 2
Subpubic Concavity: 2
Ischiopubic Ramus: 3
Judged as female but actually a male
61
I also ran discriminate function analysis on the Phenice method results as seen in
table 10 below which highlights the males incorrectly classified for sex as females.
Table 10 Casewise Statistics for sample
Discriminan
Highest Group
Second Highest Group
t Scores
P(D
>d |
P(
G=g
Squared
G=
Squared
P(G
Mahalanobis
g|
Mahalanobi
d
=g |
Distance to
D=
s Distance
f
D=d)
Centroid
d)
to Centroid
. 1
1.00
)
Case
Actual
Predicted
No
Group
Group
Origina 1
1
p
1
l
7
.073
0
Group
2 .00
Function 1
18.682
1.674
21.369
1.974
11.060
.677
18.682
1.674
18.682
1.674
0
8
8
2
1
1
. 1
5
1.00
.325
0
2 .00
0
6
9
3
1
1
. 1
.995
.529
4
2 .00
5
6
7
4
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
5
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
62
6
1
1
. 1
.941
1.801
1
2 .05
7.349
.063
11.060
.677
7.326
-1.302
22.731
-3.363
7.697
-1.370
22.131
2.056
31.577
2.971
18.682
1.674
19.958
-3.063
9
8
0
7
1
1
. 1
.995
.529
4
2 .00
5
6
7
8
1
2
**
. 1
.940
1.812
1
1 .06
0
7
8
9
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
10
2
2
. 1
.954
1.635
2
1 .04
6
0
1
11
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
12
1
1
. 1
1
1.00
2.453
0
2 .00
0
1
7
13
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
14
2
2
. 1
6
1.00
.172
0
1 .00
0
7
9
63
15
2
2
. 1
.995
.535
4
1 .00
11.031
-1.917
13.851
1.073
18.682
1.674
13.851
1.073
7.326
-1.302
18.682
1.674
16.690
-2.681
11.060
.677
11.485
-1.985
5
6
4
16
1
1
. 1
.999
.110
7
2 .00
1
4
0
17
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
18
1
1
. 1
.999
.110
7
2 .00
1
4
0
19
1
2
**
. 1
.940
1.812
1
1 .06
0
7
8
20
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
21
2
2
. 1
9
1.00
.001
0
1 .00
0
7
4
22
1
1
. 1
.995
.529
4
2 .00
5
6
7
23
2
2
. 1
.996
.441
5
1 .00
4
0
7
64
24
2
2
. 1
7
1.00
.111
0
1 .00
19.234
-2.981
16.690
-2.681
11.060
.677
18.682
1.674
9.540
-1.684
22.131
2.056
4.377
-.688
22.131
2.056
18.682
1.674
0
3
9
25
2
2
. 1
9
1.00
.001
0
1 .00
0
7
4
26
1
1
. 1
.995
.529
4
2 .00
5
6
7
27
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
28
2
2
. 1
.987
.930
3
1 .01
3
3
5
29
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
30
1
2
**
. 1
.566
3.845
0
1 .43
4
5
0
31
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
32
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
65
33
1
1
. 1
5
1.00
.424
0
2 .00
22.131
2.056
11.060
.677
16.176
1.374
16.690
-2.681
21.369
1.974
18.682
1.674
21.369
1.974
4.377
-.688
18.682
1.674
0
1
5
34
1
1
. 1
.995
.529
4
2 .00
5
6
7
35
1
1
. 1
9
1.00
.001
0
2 .00
0
7
5
36
2
2
. 1
9
1.00
.001
0
1 .00
0
7
4
37
1
1
. 1
5
1.00
.325
0
2 .00
0
6
9
38
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
39
1
1
. 1
5
1.00
.325
0
2 .00
0
6
9
40
1
2
**
. 1
.566
3.845
0
1 .43
4
5
0
41
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
66
42
2
2
. 1
4
1.00
.511
0
1 .00
22.731
-3.363
18.682
1.674
22.131
2.056
9.540
-1.684
11.060
.677
19.234
-2.981
18.682
1.674
13.851
1.073
11.060
.677
0
7
5
43
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
44
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
45
1
2
**
. 1
.987
.930
3
1 .01
3
3
5
46
1
1
. 1
.995
.529
4
2 .00
5
6
7
47
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
48
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
49
1
1
. 1
.999
.110
7
2 .00
1
4
0
50
1
1
. 1
.995
.529
4
2 .00
5
6
7
67
51
1
1
. 1
5
1.00
.424
0
2 .00
22.131
2.056
19.234
-2.981
19.234
-2.981
18.682
1.674
18.682
1.674
25.047
2.356
9.540
-1.684
18.682
1.674
16.690
-2.681
0
1
5
52
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
53
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
54
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
55
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
56
1
1
. 1
3
1.00
.906
0
2 .00
0
4
1
57
2
2
. 1
.987
.930
3
1 .01
3
3
5
58
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
59
2
2
. 1
9
1.00
.001
0
1 .00
0
7
4
68
60
1
1
. 1
5
1.00
.325
0
2 .00
21.369
1.974
9.540
-1.684
16.176
1.374
32.501
3.053
18.682
1.674
18.682
1.674
19.234
-2.981
22.131
2.056
22.731
-3.363
0
6
9
61
2
2
. 1
.987
.930
3
1 .01
3
3
5
62
1
1
. 1
9
1.00
.001
0
2 .00
0
7
5
63
1
1
. 1
0
1.00
2.716
0
2 .00
0
9
9
64
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
65
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
66
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
67
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
68
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
69
69
2
2
. 1
6
1.00
.172
0
1 .00
19.958
-3.063
19.234
-2.981
16.176
1.374
7.326
-1.302
18.682
1.674
11.060
.677
19.234
-2.981
22.731
-3.363
5.404
-.920
0
7
9
70
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
71
1
1
. 1
9
1.00
.001
0
2 .00
0
7
5
72
1
2
**
. 1
.940
1.812
1
1 .06
0
7
8
73
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
74
1
1
. 1
.995
.529
4
2 .00
5
6
7
75
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
76
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
77
2
2
. 1
.770
2.987
0
1 .23
0
8
4
70
78
1
1
. 1
9
1.00
.001
0
2 .00
16.176
1.374
18.682
1.674
25.047
2.356
18.682
1.674
22.731
-3.363
22.131
2.056
19.234
-2.981
14.221
-2.367
16.690
-2.681
0
7
5
79
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
80
1
1
. 1
3
1.00
.906
0
2 .00
0
4
1
81
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
82
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
83
1
1
. 1
5
1.00
.424
0
2 .00
0
1
5
84
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
85
2
2
. 1
.999
.079
7
1 .00
1
7
8
86
2
2
. 1
9
1.00
.001
0
1 .00
0
7
4
71
87
2
2
. 1
.770
2.987
0
1 .23
5.404
-.920
25.047
2.356
7.326
-1.302
13.851
1.073
32.501
3.053
19.234
-2.981
18.682
1.674
36.016
3.353
19.234
-2.981
0
8
4
88
1
1
. 1
3
1.00
.906
0
2 .00
0
4
1
89
1
2
**
. 1
.940
1.812
1
1 .06
0
7
8
90
1
1
. 1
.999
.110
7
2 .00
1
4
0
91
1
1
. 1
0
1.00
2.716
0
2 .00
0
9
9
92
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
93
1
1
. 1
7
1.00
.073
0
2 .00
0
8
8
94
1
1
. 1
0
1.00
3.796
0
2 .00
0
5
1
95
2
2
. 1
7
1.00
.111
0
1 .00
0
3
9
72
96
2
2
. 1
7
1.00
.111
0
1 .00
19.234
-2.981
13.715
-2.299
22.731
-3.363
22.731
-3.363
36.016
3.353
36.016
3.353
0
3
9
97
2
2
. 1
.999
.122
7
1 .00
1
2
7
98
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
99
2
2
. 1
4
1.00
.511
0
1 .00
0
7
5
100
1
1
. 1
0
1.00
3.796
0
2 .00
0
5
1
101
1
1
. 1
0
1.00
3.796
0
2 .00
0
5
1
**. Misclassified case
The results for time for both methods is shown below in table 11. The Phenice
method times ranged from 11 seconds to 4.40 minutes with a mean of 59 seconds. The
metric measurement method ranged from 1.17 minutes to 6.09 minutes with a mean of 2
min. The Phenice method was completed in half the time of the metric measurement
method which was very time consuming.
73
Table 11
Descriptive Statistics
N
Minimum
Maximum
Mean
Time
101
.11
4.40
.5943
TimeMetric
101
1.17
6.09
1.9950
Valid N (listwise)
101
74
Chapter VI
Discussion
Assessment of accuracy and reliability in sex identification methods is important
in forensic anthropology. Without an understanding of how accurate or reliable a sex
estimation method is in making sex determinations, the method lacks validity. If a
method is accurate but not reliable or vice versa reliable but not accurate it is of no use to
the researcher because it cannot produce correct classification on a repeatable basis.
Reliability
When a method produces consistent results between observations and observers it
is considered reliable. Reliability in this study is established with an intra-observer error
test. Observations were made twice by the author using a random sample of 15 using the
same skeletal materials. These results were compared using a paired t-tests in order to
determine how consistent the methods were on a repeatable basis.
Intraobserver Reliability
Observations made were highly concordant for the metric measurement method
and the Phenice method. The paired t-test showed that all metric measurements except
the iliac breadth showed no statistical significance between the two measurements per
land mark. Thus, the first and second observations are similar enough in four out of five
of the measurements that we can say there are no significant differences between them.
The Phenice method appeared to be more reliable than the metric measurement
method. The first and second round yielded almost identical results and sexed the same
13 individuals correctly and 2 individuals incorrectly. Overall, the methods were reliable
75
between the first and second observations conducted by the author but as predicted the
Phenice method was more reliable and easier to assess in the same manner on a
repeatable basis.
Accuracy
A method that can correctly classify individuals is considered accurate. A high
percentage of correctly identified individuals indicates a more accurate method than one
that misclassifies high percentages of individuals. Accuracy rates are determined in this
study by comparison of correctly classified individuals versus incorrectly classified
individuals.
The metric measurement method correctly classified 93.1% of individuals,
incorrectly classifying 2 (94.3%) of a sample of 35 females and 5 (92.4%) from a sample
of 66 males.
In regards to the accuracy of sex determination of males and females, Meindl et
al. (1985) suggests that the females’ skeleton is seldomly incorrectly diagnosed. This is
apparently due to the less variability in female pelvic size, since women are under strong
selective pressures related too adaption in locomotion as well as reproduction (Bruzek,
2002). In this study females were correctly identified more often than males.
In the Phenice method results all females (35) were determined with 100%
accuracy as opposed to males (89.4%) which gives validity to Meindl’s findings.
Although 100% of females were accurately diagnosed only 7 of 35 females were scored
as all 1’s for each of the landmark traits as seen in the figures below. So although it was
easier to determine if an individual was a female, there were still some ambiguous traits
76
present but more often than not the individual was still recognizable as a female
especially with the Phenice method.
The Phenice method accurately assessed sex for 94 of 101 individuals for an
accuracy rate of 93.1%. This suggests that the technique not only gives an accurate sex
determination but gives accuracy even with an inexperienced observer like Phenice
suggests. Although the accuracy percentage is not as high as Phenice reported in his
original study it does give validity to his technique. Perhaps the difference in accuracy
reflects the difference in experience levels of the investigator. At the time of the study,
Phenice was an advanced graduate student who had already gained experience in
examining skeletal remains in a forensic and archeological setting. The differences in
accuracy may reflect his experience level which may have played a role in his scoring of
the features in his method. Also because there is overlap in the sexes it may be that those
who show ambiguous traits or traits not specific to the norm for the actual sex will always
be present in a large sample.
This study suggest that the use of the three landmarks for sex estimation with an
inexperienced investigator produces accurate results, confirming Phenice’s assertion that
the technique does not require experienced observers to yield accurate results.
An understanding of the accuracy and reliability of any identification
method is necessary for scientific research and legal purposes. If repeated research cannot
produce repeated results, and error rates are too high, producing low percentages of
correctly classified individuals, a method will be inappropriate and of no use in both the
scientific and legal setting. If a method yields high percentages of accuracy on a
repeatable basis, that method is valid and use of that method can be justified.
77
Os Coxa Scored with all 1’s indicative of Female
Figure 37 Os coxa 21 (Female)
Figure 38 Os coxa 21 (Female)
78
Figure 39 Os coxa 86 (Female)
Figure 40 Os coxa 86: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
79
Figure 41 Os coxa 158
Figure 42 Os coxa 158: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
80
Figure 43 Os coxa 173
Figure 44 Os coxa 173 :Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
81
Figure 45 Os coxa 182
Figure 46 Os coxa 182: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
82
Figure 47 Os coxa 201
Figure 48 Os coxa 201: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
83
Figure 49 Os coxa 203
Figure 50 os coxa 203: Ventral arc, Subpubic concavity, Ischiopubic Ramus ridge
84
Male vs. Female os coxa from sample
Figure 51 Os coxa 207: Male (scored with all 5's)
Figure 52 Os coxa 182: Female (scored with all 1's)
85
Chapter VII
Conclusion
The purpose of this research was to test the usefulness of the metric vs. Phenice
method of sex estimation using the os coxa to gain a better understanding of accuracy and
reliability. It is important that osteologists know the accuracy and reliability rates of sex
estimation so a correct identification of an unknown individual can be made. Validation
studies such as this is of importance to determine rates of accuracy and reliability in sex
determination as well as identify methods that help correctly identify skeletal remains on
a repeatable basis. It is important that we understand how often an incorrect
determination can be made using these specific methods.
It is important to have a variety of sex estimation methods that utilize different
elements of the skeleton in case there are only fragmentary remains, but it is also just as
important that we utilize the methods and regions that yield the highest levels of
accuracy. Because the os coxa is the most sexually dimorphic bone in the skeleton, only
the pelvis landmarks were used for this research, however it is important to note that the
skull and long bones can also be used and should be used in addition to the pelvis if
available for the most accurate estimation of sex.
The intra-observer error study revealed a high degree of consistency between all
observations. However the Phenice method was just as accurate as the metric
measurements but on a repeatable basis. For the metric measurements there was a high
degree of concurrence between observations for all aspects including 4 of the 5 metric
measurements excluding the iliac breadth. This indicates that both methods can be used
86
reliably multiple times by the same researcher. Both of these methods demonstrate a high
degree of consistency. Although MacLaughlin (1990) stated metric measurement
methods offer advantages over visual methods because of 1. It is inherently more
objective, 2. Replicability is high, 3. It is less dependent on previous observation
experience. I did not find this to be the case in this study. I very often found it difficult to
locate the exact landmark for measurement. I also found I was not able to replicate
results. Although it is highly likely that measurements will be different each time for a
specific landmark because the measurement is taken from an estimation of the landmark
area on the bone. I found that although the measurements taken for iliac breadth were
close for the intra observer error test. The measurements for both rounds were statistically
significantly different. The landmarks for metric measurements were not easier to find on
a consistent basis.
However Phenice’s method was very easy to follow and very rarely did I
have trouble using his method. The only time questions arose was when the os coxa had
ambiguous traits which is to be expected because sexual dimorphism among males and
females is very slight in humans and there is very often overlap between the sexes. But as
Phenice (1969) noted, when there was some ambiguity concerning one, or rarely two of
the criteria, there was almost always one of the criteria which was obviously indicative of
male or female. Phenice’s method was much easier to repeat than the metric
measurements. Accuracy in determining sex of 93/1% was obtained in this study
compared to 96% reported by Phenice. Although Phenice obtained a higher percentage
using the method which may be because he had more experience, I don’t think that the
87
level of experience would change the percentage by much. Some individuals have
ambiguous features thus making it harder to estimate sex.
Of the individuals misclassified, individual 65, a white male age 73 was the only
individual misclassified using both methods. His visual landmarks and metric
measurements appeared to be female which is a prime example of the overlap between
the sexes. Sex determination is not always straight forward. Normal human variation can
produce small males as well as robust females. This is a prime example of a small male,
and without his known sex, he more than likely would have been judged incorrectly. This
shows us why it is important to utilize the other bones such as the skull, and long bones if
they are available for the most accurate assessment. It would be interesting to test if the
results would remain the same if those other bones were used as well.
Limitations in this study include the representatives of the sample and researcher
bias. While an attempt was made to obtain a sample that was representative of the
population, sex was not known at the time of measuring and scoring. This resulted in a
sample with a lot more males (66) than females (35). Additionally, the sample was not
very diverse in terms of ancestry. I wanted to use a population that was homogeneous
because I thought I would have less variance within the population. However, I think it
would be helpful to recreate this study on other populations with different ancestry to
compare results to see if levels of accuracy and reliability are comparable to these
findings among other ethnic groups.
Researcher bias may have played a part in this study as well. While the attempt
was made to limit bias, it is not always possible to assess a visual trait without also
observing other traits at the same time. When examining an os coxa, it is difficult to
88
ignore everything but the trait being analyzed, it is possible that the assessment of some
traits were influenced by the simultaneous observation of others.
Although I think a sample of 101 was more than adequate, I would have been
interested in the accuracy levels of a much larger sample. However larger samples of
documented subjects are few in numbers. Future research should utilize larger
documented skeletal collections to test both metric and Phenice methods. Accuracy was
high at 93.1% for both the metric and the Phenice method, this may not be the case for
other studies.
Although I think it is important to use all five of the metric measurements
used in this study for a complete picture it may be interesting to see the results for the
metric measurements if only the three measurements that yielded the most significant
results for association with sex are used.
Scientific research must continue to test and retest these methods on different
population samples in order to assure the most accurate and reliable sex determinations.
This thesis provided validation for methods that have been previously researched but this
research must continue to create standards for sex identification that is population
specific.
89
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95
Appendix A
Skeleton Population Statistics
Doc #
Sex
Age
Population
21
female
78
White
29
female
36
White
34
female
71
no data
37
female
78
no data
46
female
91
White
48
female
53
White
49
female
22
White
51
female
72
White
62
female
47
White
77
female
73
White
86
female
77
White
107
female
26
no data
114
female
68
White
117
female
56
no data
132
female
69
White
140
female
61
White
142
female
56
White
156
female
82
White
96
Doc #
Sex
Age
Population
158
female
50
White
159
female
72
White
160
female
68
White
172
female
85
White
173
female
73
White
175
female
63
White
182
female
74
White
184
female
79
White
185
female
62
White
186
female
101
White
187
female
81
White
192
female
72
White
196
female
83
White
198
female
39
White
199
female
98
White
201
female
53
White
203
female
69
White
4
male
52
White
5
male
62
White
6
male
41
White
7
male
71
White
97
Doc #
Sex
Age
Population
16
male
60
White
17
male
41
White
19
male
52
White
20
male
87
White
31
male
57
White
32
male
73
no data
33
male
67
no data
38
male
86
no data
39
male
81
no data
42
male
83
White
43
male
71
White
44
male
50
White
47
male
69
White
52
male
51
White
53
male
59
White
63
male
59
White
65
male
73
White
68
male
52
White
69
male
36
White
72
male
60
White
73
male
47
White
76
male
elderly
White
98
Doc #
Sex
Age
Population
80
male
58
White
81
male
73
White
83
male
24
White
84
male
68
White
85
male
59
White
87
male
74
White
95
male
60
no data
99
male
69
White
100
male
40
White
103
male
19
White
108
male
83
no data
112
male
32
White
113
male
41
White
118
male
63
White
119
male
72
White
123
male
66
White
137
male
63
White
141
male
30
White
143
male
50
White
145
male
66
White
151
male
32
White
154
male
52
White
99
Doc #
Sex
Age
Population
157
male
76
White
161
male
60
White
162
male
54
White
167
male
74
White
170
male
81
White
176
male
34
White
177
male
90 (91?)
White
179
male
77
White
180
male
78
White
183
male
58
White
188
male
56
White
189
male
69
White
190
male
61
no data
191
male
39
White
193
male
77
White
195
male
60
White
206
male
75
White
207
male
61
White
100
Appendix B
Key- Visual Measurement Data
1= Female
2=Male
Ventral Arc
1=Female
2=Probable female
3=Ambiguous
4=Probable male
5=Male
Subpubic Concavity
1=Female
2=Probable female
3=Ambiguous
4=Probable male
5=Male
Ischiopubic Ramus Ridge
1=Female
2=Probable female
3=Ambiguous
4=Probable male
5=Male
101
Phenice Method Results (original data/round 1)
Os Coxa ID
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
4
4
4
4
5
4
5
4
6
3
4
4
7
4
4
4
16
4
4
4
17
2
4
5
19
3
4
4
20
2
2
3
21
1
1
1
29
3
1
1
31
4
4
5
32
5
5
4
33
4
4
4
34
1
2
1
37
1
2
4
38
4
2
4
39
4
4
4
42
4
2
4
43
2
2
3
44
4
4
4
102
Os Coxa ID
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
46
1
2
2
47
3
4
4
48
2
1
2
49
1
1
2
51
1
2
2
52
3
4
4
53
4
4
4
62
2
2
2
63
4
4
5
65
3
2
2
68
4
4
5
69
4
4
4
72
4
4
4
73
3
4
4
76
4
3
4
77
1
2
2
80
4
5
4
81
4
4
4
83
4
5
4
84
3
2
2
85
4
4
4
86
1
1
1
95
4
4
4
103
Os Coxa ID
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
99
4
4
5
100
2
2
2
103
3
4
4
107
1
1
2
87
4
4
4
108
4
2
4
112
3
4
4
113
4
4
5
114
1
1
2
117
1
1
2
118
4
4
4
119
3
4
4
123
4
5
5
132
2
2
2
137
4
4
4
140
1
2
2
141
4
5
4
142
2
2
2
143
4
3
4
145
5
4
5
151
4
4
4
154
4
4
4
156
1
1
2
104
Os Coxa ID
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
157
4
4
5
158
1
1
1
159
1
2
1
160
1
1
2
161
4
3
4
162
2
2
3
167
4
4
4
170
3
4
4
172
1
1
2
173
1
1
1
175
2
2
4
176
4
3
4
177
4
4
4
179
4
5
5
180
4
4
4
182
1
1
1
183
4
4
5
184
1
1
2
185
2
1
1
186
1
2
2
187
2
2
4
188
4
5
5
189
2
2
3
105
Os Coxa ID
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
190
4
2
4
191
5
4
5
192
1
1
2
193
4
4
4
195
5
5
5
196
1
1
2
198
1
1
2
199
1
2
3
201
1
1
1
203
1
1
1
206
5
5
5
207
5
5
5
106
Phenice Method Results Round 2 for intra-observer error test: Random sample of 15.
Os coxa No.
Ventral Arc
Subpubic Concavity
Ischiopubic Ramus Ridge
42
4
2
4
52
4
4
4
53
4
4
4
69
4
4
4
73
4
4
4
81
4
4
4
84
3
2
2
87
4
4
5
95
4
4
4
100
2
2
2
113
4
4
5
137
4
4
4
154
4
4
4
157
4
4
5
161
4
3
4
107
Appendix C
Metric Measurement results (original data/round 1)
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch
4
222.00
162.94
86.37
93.64
37.76
5
210.85
160.14
93.00
95.60
38.95
6
204.25
154.06
88.67
90.07
39.28
7
220.66
153.97
89.24
88.44
34.03
16
230.65
169.06
91.86
92.47
45.27
17
214.52
169.00
89.69
91.77
38.52
19
217.75
154.11
88.44
85.96
41.34
20
218.51
154.09
94.43
87.97
36.66
21
188.71
148.03
75.58
76.07
32.75
29
199.12
136.87
77.78
70.67
42.94
31
215.43
160.53
82.29
86.24
42.35
32
225.85
151.21
88.52
86.18
38.23
33
218.50
154.04
88.21
95.63
34.92
34
193.46
143.42
91.65
76.24
34.90
37
217.65
147.37
94.39
79.18
31.61
38
230.05
166.00
92.78
85.33
38.35
39
232.44
167.41
90.09
90.10
38.75
42
198.99
140.04
84.55
77.02
35.37
43
215.42
140.04
84.55
77.02
40.64
108
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch
44
229.92
168.38
92.15
92.62
37.32
46
214.75
164.78
90.37
76.29
33.95
47
208.07
148.02
84.26
76.06
31.92
48
205.16
161.71
93.05
80.51
37.08
49
210.14
164.58
93.21
84.09
39.38
51
221.91
154.14
95.06
83.03
33.93
52
223.29
154.12
91.69
92.16
41.45
53
232.56
166.09
101.77
99.67
25.80
62
204.13
159.95
91.87
83.21
45.20
63
216.41
154.12
93.73
88.20
38.73
65
222.95
168.73
96.67
82.39
30.77
68
229.89
165.10
94.89
93.76
39.33
69
217.39
153.42
85.69
90.50
31.98
72
212.49
153.63
85.25
81.84
38.70
73
241.02
166.34
91.17
90.85
39.64
76
220.96
174.27
95.40
87.98
45.53
77
205.49
140.62
92.24
78.02
31.51
80
241.02
166.34
106.45
96.07
42.96
81
214.65
164.14
95.88
89.12
39.59
83
226.92
158.96
93.55
84.92
41.32
84
229.82
165.50
98.80
95.27
41.25
109
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch
85
215.36
166.12
89.24
89.20
36.65
86
186.44
152.85
87.45
72.16
41.35
95
226.30
160.84
86.43
89.93
41.43
99
226.32
169.27
89.35
85.98
43.83
100
232.57
172.82
99.00
95.26
44.75
103
214.18
151.52
84.53
85.85
46.95
107
211.74
153.55
93.75
82.13
48.30
87
235.10
169.44
96.31
90.52
38.90
108
211.89
162.89
95.70
84.99
42.54
112
216.05
152.94
87.21
84.02
45.21
113
242.97
168.91
93.19
90.72
45.37
114
206.12
148.40
90.44
79.51
46.12
117
208.39
165.56
92.79
78.02
47.15
118
232.12
168.10
96.41
88.30
42.15
119
209.28
142.92
84.21
83.15
43.58
123
211.64
152.72
90.87
84.77
45.84
132
211.55
159.70
91.08
83.62
46.00
137
238.88
165.95
100.25
100.55
47.74
140
193.35
160.44
85.89
77.15
37.30
141
197.85
146.69
86.96
78.73
42.26
142
190.63
145.81
89.07
75.36
43.70
110
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch
143
222.47
164.70
95.48
90.80
40.40
145
214.53
154.15
88.02
85.88
43.55
151
220.90
154.03
96.82
90.48
47.81
154
220.56
164.55
90.42
88.15
42.52
156
188.14
143.14
90.31
76.07
40.57
157
244.32
167.15
92.50
87.79
42.21
158
164.48
127.89
79.27
55.30
32.64
159
199.47
153.74
96.16
78.85
39.07
160
165.30
153.34
87.76
73.29
44.29
161
222.46
158.56
89.68
87.93
39.96
162
213.89
154.12
91.54
85.27
45.76
167
234.87
161.37
93.00
93.48
46.15
170
218.40
163.64
86.29
83.16
42.99
172
214.13
157.93
97.91
84.47
37.04
173
189.40
147.93
86.92
75.50
42.94
175
198.52
164.51
100.22
82.40
41.45
176
225.61
161.33
97.34
91.73
48.12
177
217.82
154.16
84.31
85.29
42.28
179
221.16
167.57
97.82
96.71
33.02
180
216.30
158.07
88.64
88.73
47.29
182
191.75
147.17
89.44
70.01
33.05
111
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch
183
228.18
157.85
90.79
91.92
46.44
184
213.74
154.19
101.00
82.19
44.33
185
193.00
147.63
90.10
76.45
32.79
186
207.81
148.67
80.23
76.62
34.40
187
197.68
147.92
92.94
75.20
33.92
188
241.49
169.50
98.22
94.51
41.35
189
226.64
158.26
97.81
91.50
43.27
190
214.52
157.88
92.19
83.56
44.03
191
213.25
152.28
89.22
80.79
40.81
192
195.90
156.49
80.48
77.25
34.41
193
218.91
158.13
90.81
85.58
40.37
195
232.26
161.99
97.78
89.56
38.25
196
197.56
151.42
91.79
76.84
44.48
198
210.86
151.90
91.44
76.23
36.60
199
213.81
157.44
98.79
81.46
31.71
201
195.51
142.09
91.01
77.57
34.33
203
210.00
155.83
94.03
80.06
40.93
206
217.37
167.07
96.31
89.78
40.20
207
233.00
164.24
96.09
92.73
41.24
112
Metric Measurement results round 2 for intra-observer error test
Os Coxa ID
Os coxa H
Iliac Breadth
Pubis
Ischia
Greater
Length
Length
Sciatic
Notch Width
42
200.44
140.49
83.34
77.32
35.87
52
221.94
154.13
90.90
91.25
42.08
53
235.08
164.69
100.20
100.17
26.27
69
215.98
151.58
87.18
89.60
30.96
73
239.10
165.19
93.88
92.61
37.21
81
218.67
161.80
94.06
93.24
39.85
84
226.58
163.14
96.79
95.44
41.77
87
233.71
167.84
98.57
93.35
39.30
95
227.25
162.46
90.47
91.33
37.68
100
230.80
171.68
103.15
96.30
45.27
113
240.08
165.69
95.28
87.43
43.13
137
240.91
164.35
99.88
99.05
49.47
154
221.53
162.32
92.95
90.35
39.32
157
230.57
162.20
94.12
95.42
45.84
161
230.27
160.94
96.82
93.57
41.44
113