1. Chapter 8 Causal-Comparative Research Gay, Mills, and Airasian
Educational Research
Chapter 8
Causal-Comparative Research
Gay, Mills, and Airasian

2. Topics Discussed in this Chapter
The purpose of causal-comparative research
Comparisons with other designs
Design issues and procedures
Control
Data analysis and interpretation

3. Purpose
Attempts to determine the cause for preexisting differences in groups of individuals
Groups already differ on some variable and the researcher attempts to identify a major factor that led to these differences
Students participating in extracurricular activities have higher grade point averages than students who do not participate
Children who attend preschool are more adjusted socially in the first grade than those children who do not attend preschool
Objective 1.1

4. Purpose The alleged cause and effect have already occurred
Orientations
Retrospective - starts with an effect and seeks possible causes
Prospective - starts with a cause and investigates its effect on some variable
Objectives 1.1 & 1.2

5. Similarities to Correlational Research
Both lack manipulation
Both require caution in interpreting results
Both can support subsequent experimental research
Objective 2.1

6. Differences from Correlational Research
No attempt to understand cause and effect
Two variables, one is a predictor and one a criterion
One group
Involves relationships
Causal comparative
Attempt to understand cause and effect
At least one independent variable (i.e., purported cause) and one dependent variable (i.e., purported effect)
Two or more groups
Involves comparisons
Objective 2.2

7. Comparison to Experimental Research
Causal group comparisons
Individuals randomly assigned to treatment groups
Independent variable manipulated by the researcher
Causal comparative
Group comparisons – but not causal
Individuals already in groups before research begins
Independent variable not manipulated
Cannot
Should not
Is not
Objectives 3.1 & 3.2

8. Examples of Non-Manipulated Variables
Age
Sex
Ethnicity
Learning style
Socioeconomic status
Parental educational level
Family environment
Preschool attendance
Type of school
Objective 3.3

9. The Value of Causal-Comparative Research
Permits the investigation of variables that cannot or should not be manipulated
Can inform decisions
Results can lead to experimental studies that establish causality
Very cost effective to conduct
Objective 3.4

10. Design The basic design is an experimental-control group posttest only
(E) X O
(C) O
An alternative design is a comparison group posttest only
(E) X1 O
(C) X2 O
Objective 4.1

11. Procedures Select two groups that differ on some independent variable
One group possesses some characteristic that the other does not
Each group possesses the characteristic but in differing amounts
The independent variable must be clearly operationally defined
Objective 4.3

12. Procedures Randomly sample subjects from each of the two groups
Collect background information on subjects to help determine the equality of the groups
Compare groups on the dependent variable
Objective 4.3

13. Control of Extraneous Variables
Lack of randomization, manipulation, and control are all weaknesses of causal comparative designs
Three ways to control extraneous variables
Matching – pair-wise matching of subjects on a variable likely to influence performance
Two subjects – one from each group - with similar scores on the matching variable are matched and included in the sample
Limited by the potential lack of matches
Objectives 5.1, 5.2, & 5.3

14. Control of Extraneous Variables
Three ways to control (cont.)
Comparing homogeneous groups – create groups that are similar on an important extraneous variable
Limited by a potentially restricted range of scores on the extraneous variable
An alternative is to form subgroups within each group to accommodate a larger range of scores on the extraneous variable
The use of factorial analysis of variance (ANOVA) to analyze the interaction between the independent variable groups and the extraneous variable subgroups
Objectives 5.2, 5.4, 5.5, & 5.6

15. Control of Extraneous Variables
Three ways to control (cont.)
Analysis of covariance (ANCOVA)
Statistically adjusting the scores on the dependent variable for differences on an extraneous variable of importance
Limited by the need to strictly adhere to the statistical assumptions of ANCOVA
Objectives 5.2 & 5.7

16. Data Analysis Descriptive statistics Inferential statistics
Central tendency
Mean
Median
Mode
Variation
Standard deviation
Inferential statistics
t test
ANOVA
ANCOVA
Chi square
Objective 5.8 & 5.9

17. Interpretation of Data
Difficulty establishing cause and effect requires caution in interpreting results
No manipulation of the independent variable has occurred
No randomization
Minimal control of extraneous variables
Objective 6.1

18. Interpretation of Data
Causality and alternative explanations
Order of causation
Reversed causality – difficulty establishing which variable is the cause and which is the effect
Does attitude affect achievement or achievement affect attitude?
Order of occurrence can often be determined logically
Gender can affect social development in young children but social development cannot affect gender
Attending preschool can affect kindergarten performance but kindergarten performance cannot affect preschool attendance
Different causal variable – equate groups on a potential causal variable
Objectives 6.2 & 6.3