15_Validity2 - Validity 2 Protecting Internal Validity,...

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Validity 2 Protecting Internal Validity, Describing External Validity, and the In-Basket Example
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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
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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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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
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Review Describe the 3 good designs for protecting internal validity Randomized pretest-posttest Solomon Four Group Randomized Posttest Only How are the three related?
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15_Validity2 - Validity 2 Protecting Internal Validity,...

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