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Differential (Casual-comparative) Research. Definition – Research design in which behavior is measured in 2 groups that differ on 1 primary variable. The “IV” (not true IV) is the ________ or ______variable Classification variable is not manipulated because it is _______ or ___________
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Differential (Casual-comparative) Research Definition – Research design in which behavior is measured in 2 groups that differ on 1 primary variable. • The “IV” (not true IV) is the ________ or ______variable • Classification variable is not manipulated because it is _______or___________ • Normal adults vs. psychopaths • history of abuse vs. no history • Males vs. females • heroine abusers vs. polydrug abusers Does Group A differ from Group B on measures of the DV?
Differential (Casual-comparative) Research Intact Group of Participants Intact Group of Participants Measurement of the Dependent Variable Measurement of the Dependent Variable
Differential (Casual-comparative) Research Does ____ demonstrate a causal relationship • There is no guarantee that the two groups will be ______________ in all other ways. • There may be ________________ explanations for the observed differences. e.g., kids who play sports vs. those who don’t – compare measures of academic success.
Conducting differential (causal-comparative research • Select groups that vary on __ quantifiable variable • Requires ________ definitions • Matching participants – equate groups on ______________factors • Select _____________ groups – more likely to see difference in variable of interest
Two groups that differ on some dimension 10 children w/severe behavior problems 10 children w/no behavior problems Compare the two groups Avg. IQ = 103 Avg. IQ = 104 Avg. # hobbies = 4 Avg. # hobbies = 3 Avg. # siblings = 4 Avg. # siblings = 1 History of abuse = 6/10 History of abuse = 3/10 Relationship?
Two groups that differ on some dimension 20 smokers 20 nonsmokers Compare the two groups Ed. = High school Ed. = High school Avg. # drinks/day = 2 Avg. # drink/day = 3 15/20 single 5/20 married 3/20 single 17/20 married Relationship?
Developmental Research Designs – study age-related changes in behavior Cross-sectional research design • Measure a variable in different ___________ • Like a ____________ group design • Cannot determine how any ___________ changes • Other factors may influence groups other than age (______/_____________ effects) Age group 1 e.g., 2-3 Age group 2 e.g., 4-5 Age group 3 e.g., 6-7