Types of Group Designs ____________ group design. The experiment compares groups that receive or _______________ the IV (control group) e.g., behavior is studied in 2 groups who have been given a medium dose of alcohol or placebo Control group is the _______________group Control group rules out internal validity threats Participants should be randomly __________ from the population (if possible) Participants in the sample should be randomly __________________ to groups or matched to prevent assignment bias Lect 11a

When would you want to use a control group design? Control group designs are used when: You want a comparison group that does ____receive any level of the IV e.g., the effects of hormones on aggression. Ovary removal in lizards. Common in clinical studies where a new ______________ is being investigated e.g., the effects of new drug on weight loss. Lect 11a

Control-group Design Sample Drawn Randomly from Population Random Assignment of Participants to Conditions IV NO IV (Control) Measurement of the Dependent Variable Measurement of the Dependent Variable Lect 11a

What does comparing to a control group tell us? Post-test Pre-test Conduct Experiment Functional Relationship? Lect 11a

What does comparing to a control group tell us? Post-test Pre-test Conduct Experiment Functional Relationship? To demonstrate a functional relationship, the experimental group should show a change but the control group should ______________. This rules out the possibility that ________________ caused the effect. Lect 11a

Types of control groups _______________ ________ control group – participants led to believe they are receiving some treatment although they are not. (placebo = pharmacologically _______ substance) ________ control – those in control group eventually given treatment. Used in research designed to assess the effectiveness of treatment program. Control group receives ________________, other group receives experimental treatment Lect 11a

Control-group designs Common control-group designs ____________ control group design ___________ control group design ____________ group design Lect 11a

Pretest-Posttest Control-Group Design Lect 11a

Pretest-Posttest Control-Group Design Pre-test – provides some info about group ____________ Data analysis: pre vs. pre / post vs. post ________________ on control group allows you to rule out internal validity threats: history, maturation, regression if they were affecting behavior, the control group should also show an effect Disadvantage: _________ threat Lect 11a

Posttest-Only Control-Group Design Lect 11a

Posttest-Only Control-Group Design Used when pre-tests are __________ or when they might ____________treatment (testing threats) Data analysis: post vs. post Threats to internal validity (maturation, history, instrumentation reduced by control group because their effects should be _______ in both groups) Disadvantage: cannot determine group ____________ Lect 11a

Solomon Four-Group Design Lect 11a

Solomon Four-Group Design _____ groups Combines _____________ and __________ designs Controls for __________ threats - allows you to see what effects testing has on behavior Data analysis: Multiple comparisons pre vs. pre post vs. post pre vs. post, etc... Disadvantage: many groups – study requires_____ subjects and is more difficult to conduct. Lect 11a