4.22.08 - QUASI-EXPERIMENTS Some history Campbell &...

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QUASI-EXPERIMENTS Some history Campbell & Stanley”s famous 1963 paper “Experimental & quasi- experimental designs for research on teaching” in effect gave psychologists permission to: do research outside the laboratory cope with various threats to validity in less well controlled research Campbell & Stanley’s X-O notation for designs: X O “one-group, posttest only” = demonstration only X O O “posttest only with nonequivalent control group” O 1 X O 2 “one-group, pretest-posttest” = simple within-subject design O 1 X O 2 O 1 O 2 How this last quasi-experiment addresses six threats to internal validity: Compare the pretest scores of the two groups. If similar, this reduces our concern about selection bias and regression confounds. Compare the pretest and posttest scores of the control group. If similar, this reduces our concern (some) about history and maturation . Testing
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4.22.08 - QUASI-EXPERIMENTS Some history Campbell &...

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