Advantages of Within Group
Analysis of Race/Ethnicity
KEITH E. WHITFIELD, PH.D.
VICE PROVOST FOR ACADEMIC AFFAIRS
PROFESSOR OF PSYCHOLOGY AND NEUROSCIENCE
RESEARCH PROFESSOR OF MEDICINE
CO-DIRECTOR OF CENTER ON BIOBEHAVIORAL HEALTH
DISPARITIES RESEARCH
Health Disparities
 Compared to Caucasians, African Americans
experience higher rates of:
Hypertension
 Diabetes
 Obesity
 Fatal stroke
 Heart disease death
 End-stage kidney disease

 African Americans have a lower life expectancy
rate than the overall population.

70.2 years compared to an average of 76.5 years for all
population groups.
Model of Individual Variability in Health
Social
Environment
Individual’s
Causal Field
Behavior/
Genetic
Racial
Discrimination
Social Support
Neighborhood
Access to
Medical Care
Health Disparities
Chronic Conditions
Mental Health Status
What is the question??
 How do we typically understand minority
populations?

Comparing the minority group to majority
 Comparisons are conducted in pursuit of
understanding health in minorities
 But is that what is really learn from comparison
research?
Between Group Comparisons
 Mean Differences
• Reasonable elementary step toward understanding group
differences
 Variance Differences
• Underlying distribution
• Assess invariance between groups
• May need to covary other critical factors
10
10
8
8
6
6
4
4
2
2
0
0
60
70
80
90
100
60
RA0C1(1):RESPONDENT AGE
70
80
90
100
RA0C1(1):RESPONDENT AGE
Caucasians
African Americans
Composite of verbal IQ scores and items from the Short portable Mental
Status Questionnaire from Americans Changing Lives
Statistical analyses of homogeneity reveal significant difference in the
patterns of variability between the groups.
Sample size- the power to detect differences
 The power to detect differences is perhaps one of the most
formidable challenges in comparison research.
 Samples need to be more than just representative in size to
the population from which they are drawn.


The variances need to be equivalent and the sample size needs to be
sufficient to detect differences.
Over sampling so the groups are equivalent in size.
 The challenge typically involves getting sufficient numbers
of ethnic minorities to participate.
The ratio of African Americans to Caucasians is 1 to 2
The ratio of African Americans to Caucasians is 1 to 4
The ratio of African Americans to Caucasians is 1 to 6
Measurement Issues and Error
 Precision is a measure of how close a parameter estimate is
expected to be to the true value of the parameter
(Rosenthal et al, 2000).
 Precision is then driven by the smaller of the groups.
 Scientists must assure that the instrument used to measure
the construct of interest has the same meaning across
groups including measurement error and equivalence
across groups .

Need measures that are not bias by cultural factors
Models of Cultural Differences
(Cauce, Coronado & Watson, 1998)
 Cultural Deviance Model
Differences or deviations between groups are seen as
deviant and inferior.
 Cultural Equivalence Model
 Superior socioeconomic status has provided
advantages.
 Deviant perspective attributed advantages to culture.
 Cultural Variant Model
 Resilience in the face of oppression
 Adaptation and survival due to external forces
 Culturally rooted, internal explanations for differences

Equivalence of Measures
Cauce et al., 1998
 Cultural Equivalence
• Extent the measure has same internal structure and
meanings within and across groups
 Conceptual Equivalence
• Content of items is defined similarly across groups
• Items are equally familiar across groups
Equivalence of Measures (cont.)
 Linguistic Equivalence
• Language of items is understood the same across groups
(e.g. Blue)
 Functional Equivalence
• Scores have similar correlates across groups
 Scalar Equivalence
• Scores reflect the same level of the construct across
groups
Interpreting Results
 Differences can mean strengths
 Trajectories of change may be different
 the more assessment points the better
 Including a measure of ethnicity (e.g.,
acculturation) can be used to examine mediate
or moderating effect between groups
Within-Group Individual Differences
 Strengths
• Understand variability in measure specific to group.
• Error of measurement limited to measure and not
ethnicity
 Weakness
• Limited description of phenomena can be made—
description specific to minority group
 Should between group research be done?
 Which should come first between or within
group studies??
 Is there cases when within group analyses is
not appropriate?
Genes and Health Disparities
 Prevalence of some risk genetic alleles may differ by
race/ethnicity.
 Environmental context can differ markedly across all
disparities populations
 Search for possible gene X environment interactions
Ways Interactions can happen
Environmental
Risk Factor
Genotype
Environmental
Risk Factor
Genotype
Disease
Genotype
Environmental
Disease
Risk Factor
Genotype
Genotype
Environmental
Risk Factor
Disease
Disease
Environmental
Risk Factor
Disease
Ottman, R. (1996). Gene-Environment Interaction: Definition and study design,
Preventive Medicine, 25, 764-770.
Summary
 Studying minorities offers unique opportunities not yet
fully appreciated by many researchers

Understand how social and psychological factors impact health.
 Future research that accurately and appropriately utilizes
minorities for understanding medical conditions will
advance the field.
 Alternative strategies to studying minorities will help
advance an understanding of minorities and all people.
 More than one way to skin a cat!