Aim: What types of data and
studies exist?
HW#1: Complete last slide on loose
leaf
New Term
• Grading:
– Exams/Quizzes/Articles/SPSS 85%
• Final Exam 15% (MP3)
– Class participation 5%
• Assignments given at the end of lessons must be
submitted THAT DAY and will be part of class
participation grade
– Homework 10%
• Late homework WILL NOT be accepted
Exploratory Data Analysis
• Chapter 1 and 2 we learned about data analysis
• Exploratory Data Analysis: we rely heavily on
plotting the data
– We look for patterns that suggest interesting
conclusions or questions for further study
• However, exploratory analysis alone can rarely
provide convincing evidence for its conclusions,
because striking patterns we find in data can arise
from many sources
What is anecdotal data?
• Anecdotal evidence is based on haphazardly
selected individual cases, which often come to
our attention because they are striking in
some way.
• Anecdotal data are stories; this is when
people use their intuition or personal
experiences as data.
How reliable is anecdotal data?
• Does not provide proof but may assist
research efforts
– These cases need not be representative of any
larger group of cases.
– Can provide quantitative data
• Can get anecdotal evidence from personal
interviews, public hearings, and surveys.
Available data
• Available data are data that were produced in
the past for some other purpose but that may
help answer a present question
Example: At the Web site of the National Center for Education
Statistics, nces.ed.gov/nationsreportcard/mathematics, you
will find full details about the math skills of schoolchildren in
the latest National Assessment of Educational Progress.
Mathematics scores have slowly but steadily increased since
1990. All racial/ethnic groups, both men and women, and
students in most states are getting better in math.
What is an Experimental Study?
• In experiments, researchers give treatments
and observe to see if they cause changes in
behavior.
• A classic simple experiment is one in which a
researcher forms two groups at random and
gives each group a different treatment
*Random Assignment will be spoken about in
the next few class sessions*
Example of Experimental Study
• Fifty students were divided into groups at
random. One group received math instruction
via a correspondence course on the Internet.
The other group was given instruction on the
same math skills using a traditional textbook.
The purpose was to see if instruction via the
Internet was more effective than traditional
textbook instruction.
Characteristics of an Experimental
Study
• Experimental Group: the group of participants
receiving the treatment
– From Example: the group receiving the new type
of instruction via the internet
• Control Group: the group not receiving
treatment
– From the Example: the group receiving the
instruction with a textbook
What is a Nonexperimental Study?
• In a nonexperimental study, researchers do not
give treatments; rather they observe participants
in order to describe them as they naturally exist
without experimental treatment
– Researchers are using ways to observe participants in
order to determine their attitudes, beliefs, and
behaviors as they exist without experimental
intervention
• Come in many forms
– Example: surveys, interviews and questionnaires
Purpose of Experiments?
• The purpose of an experiment is to explore
cause-and-effect relationships (i.e. treatments
are given to see how they affect the
participants)
– ALTHOUGH nonexperimental studies can also be
used for this purpose sometimes!
Class Work: Find some available data
1. Visit the Internet and find two different examples of
available data that is interesting to you. Explain how the
data were collected and what questions the study was
designed to answer.
2. Suppose you read that an outbreak of intestinal disorders
occurred in a town and the source was traced to
contaminated chicken served in a popular restaurant. Is it
likely the study that identified the source was
“experimental’ or ‘nonexperimental?” Why?
3. Suppose you want to now whether having parents read to
preschool children has a positive effect on the children’s
subsequent reading achievement. Do you think it would
be better to conduct an experimental study or
nonexerpimental study? Why?
Homework
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Are there treatments in nonexperimental studies?
In an experiment, Group A was given verbal praise for being on time for
appointments while Group B was given no special treatment. Which group is the
control group?
What is the purpose of a nonexperimental study?
Is it necessary to have at least two groups of participants in order to conduct an
experiment?
Is a survey an experiment?
Does knowing that a multiple choice test was used in a study help a consumer of
research determine whether the study was experimental or nonexperimental?
What is the purpose of an experimental study?
A political scientist polled voters to determine their opinions on a decision by the
Supreme Court. Is this an “experimental study” or “nonexperimental study?”
A teacher compared the effectiveness of three methods of teaching handwriting
by using different methods with different students. Did the teacher conduct an
“experimental study” or “nonexperimental study?”