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Types of Group Designs

Types of Group Designs. _________-subject design . The experiment compares _____ group across different levels of the IV. e.g., behavior is studied in 1 group that is given placebo, low, medium, and high doses of alcohol. WITHIN-SUBJECTS DESIGNS. Within-subject design:

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Types of Group Designs

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  1. Types of Group Designs _________-subject design. The experiment compares _____ group across different levels of the IV. • e.g., behavior is studied in 1 group that is given placebo, low, medium, and high doses of alcohol. Lect 10c

  2. WITHIN-SUBJECTS DESIGNS • Within-subject design: • Sometimes called a _______________design • _____ large group • Random selection (usually) • All subjects experience _____ conditions • No _________________treatment • _______ exposure to conditions - no stability • ___________ statistics used to analyze mean effects • Subjects may not experience conditions in the same ______ • Can involve 2 or _____ levels of the IV Lect 10c

  3. Within-subject design, single factor Group A: Level 1 of IV Group A: Level 2 of IV • Same group examined under ____ levels of IV • Data usually analyzed used _____________ Lect 10c

  4. Within-subject, multilevel-designs Group A: Level 1 of IV Group A: Level 2 of IV Group A: Level 3 of IV • Same group examined under ____________ of IV • Data usually analyzed used repeated-measures ______. • Example: Craik and Tulving (1975) investigated whether different word-processing strategies affected memory. Asked questions before showing subjects words. Questions focused on visual properties, auditory properties, and semantic properties. (18%, 78%, 96%) Lect 10c

  5. How do within-subject design differ from a single-subject design? Single-subject design ______ n Repeated measures within each condition Conditions run until _____ Each participant’s behavior is evaluated against their ____ behavior under other conditions Individualized treatment ______ analysis of data Within-subject design _______ n One measure under each condition ____ exposure to condition A group’s average behavior under a condition is evaluated against the ____ group’s average behavior under other conditions No individualized treatment _____ analysis of data Lect 10c

  6. How do within-subject design differ from a single-subject design? IV level 1 IV level 2 IV level 3 Single-subject design Subject #1 Subject #1 Subject #1 IV level 1 IV level 2 IV level 3 Within-subject design Group #1 Group #1 Group #1 Lect 10c

  7. How do within-subject design differ from a between-subject design? Within-subject design Moderate n ____ group A group’s average behavior under each condition is evaluated against the same group’s average behavior under other conditions Between-subject design Large n ______ groups Average behavior of a group exposed to one condition is evaluated against the average behavior of another group exposed to a different condition Lect 10c

  8. How do within-subject design differ from a between-subject design? IV level 1 IV level 2 IV level 3 Between-subject design Group #1 Group #2 Group #3 IV level 1 IV level 2 IV level 3 Within-subject design Group #1 Group #1 Group #1 Lect 10c

  9. WITHIN-SUBJECTS DESIGNS • Advantages of Within-subject designs over Between-group designs: • Main advantage ---Eliminates problems of individual ___________ • Individual differences between groups cannot confound the study • You can measure treatment effects independent of individual differences • Fewer _____________ than between group Lect 10c

  10. WITHIN-SUBJECTS DESIGNS • Disadvantages of Within-subject designs: • ___________ • ______-related problems • History, Maturation, Instrumentation, Statistical regression • ________ effects – behavior may be influenced by earlier experiences in the study • __________ effects- changes in behavior caused by earlier treatment condition • __________________ – behavior changes as a function of experience - repeated testing (practice and fatigue) Lect 10c

  11. WITHIN-SUBJECTS DESIGNS- _____________________ • Method of dealing with time-related threats • Subjects receive treatments in a ______ order • e.g., Reverse counterbalancing: AB, BA • e.g., Complete counterbalancing: In a study with 3 conditions (A, B, C) subjects may be exposed to: ABC, ACB, CBA, CAB, BCA, or BAC • _____ numbers of participants get each possible sequence • Prevents order effects from __________________ particular condition Lect 10c

  12. No order effect 6 pt difference

  13. No order effect Order effect (+ 5) 6 pt difference 11 pt difference

  14. Order effect without counterbalancing Order effect with counterbalancing 11 pt difference 6 pt difference

  15. Problems with counterbalancing • Can increase _____________ within a treatment • Different treatments may produce different order effects – _________________ order effects. • Complete counterbalancing requires ______________ • May use _____ counterbalancing to at least ensure that each condition is experienced by a group first, second, third, etc. Lect 10c

  16. Summary of Single-Factor (one IV) Group Designs • Between-subject designs • 2 levels • Multilevel • Control-group designs • Pretest-posttest control group design • Posttest only control group design • Solomon 4-group design • Within-group designs • 2 levels • Multilevel Lect 10c

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