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Chapter 9 Casual-Comparative Research (value of CC (Permits the…
Chapter 9
Casual-Comparative Research
Purpose: 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
The alleged cause and effect have already occurred
Retrospective - starts with an effect and seeks possible causes
Prospective - starts with a cause and investigates its effect on some variable
comparison with
Correlational Research
Similarities
Both lack manipulation
Both require caution in interpreting results
Both can support subsequent experimental research
Differences
Correlational: No attempt to understand cause and effect
Causal Comparative: attempt to understand c&e
Correlational: Two variables, one is a predictor and one a criterion
CC: at least one IV and one DV
C: one group
CC: two or more gruops
C: involves relationships
CC: involves comparison
comparison with
Experimental Research
E: causal group comparisons
CC: group comparisons; not causal
E: random assignment to treatment groups
CC: alrdy in groups
E: IV manipulated
CC: IV not manipulated (cannot; should not; is not)
value of CC
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
Design
experimental-control group posttest only:
grp 1: treatment --> post test
grp 2: no treatment --> post test
comparison group posttest only
grp 1: treatment 1 --> post test
grp 2: treatment 2 --> post test
selection of two groups:
Collect background information
on random subjects in each group
to help determine the
equality of the groups
presence vs absence of characteristic
degree of characteristics
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
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
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
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
Causality and alternative explanations
Order of causation
Reversed causality – difficulty establishing which variable is the cause and which is the effect
e..g. Does attitude affect achievement or achievement affect attitude?
Order of occurrence can often be determined logically
e.g. Gender can affect social development in young children but social development cannot affect gender
e.g. Attending preschool can affect kindergarten performance but kindergarten performance cannot affect preschool attendance