Notes15 - Validity 2 Protecting Internal Validity,...

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1 Validity 2 Protecting Internal Validity, Describing External Validity, and the In-Basket Example Protecting Internal Validity 1. Design 1:Pretest-posttest control group design R O1 O2 R O3 X O4 R = random assignment; O = measurement or observation; X = treatment. Controls for History, Maturation, Testing & Regression. Checks on Mortality but not Instrumentation. Pretest allows view up front. Random assignment is always your first choice for internal validity. Time Protecting Internal Validity (2) • Solomon Four-Group Design R O1 O2 R O3 X O4 R O5 R X O6 World’s best design for control (but maybe not analysis). Same as pretest-posttest, but 2 more groups with no pretest. Last 2 groups will not have Testing confound. Design 2
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2 Protecting Internal Validity (3) • Randomized posttest only design. R O5 R X O6 Because of random assignment, this is a good design, even though there is no pretest. R O1 O2 R O3 X O4 R O5 R X O6 Design 3 Design 2 Design 1 Design 3 Review • Describe the 3 good designs for protecting internal validity – Randomized pretest-posttest – Solomon Four Group – Randomized Posttest Only
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This note was uploaded on 05/21/2011 for the course PSY 3213 taught by Professor Staff during the Fall '08 term at University of South Florida - Tampa.

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Notes15 - Validity 2 Protecting Internal Validity,...

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