SP_08_Variables_T-tests__ANOVA

2 3 4 if the program is effective we want no group

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Unformatted text preview: ferences at posttest Change in program group from pre to post 80 75 70 65 60 55 50 45 40 35 30 Pretest Posttest r+behmod r only Make up some numbers pretest MEAN 49 47 posttest MEAN 50 35 pretest STD DEV 6.9 7.0 posttest STD DEV 7.5 7.3 Control Program Between subjects = comparing different people Within subjects = comparing the same people Two kinds of ttests 1. Independent samples ttest: = BETWEEN SUBJECTS If different subjects are in different groups 1. Paired samples ttest: If the same subjects are measured twice = WITHIN SUBJECTS NOTE: ANY TIME YOU USE A PREPOST TEST DESIGN YOU HAVE A WITHIN SUBJECTS DESIGN BOTH kinds: Can only look at 2 levels in one independent variable at time (e.g. more than 2 need to break it up in separate analyses) 80 75 70 65 60 55 50 45 40 35 30 Independent Samples Comparison Program Pretest Posttest Independent Samples Different people in comparison and program groups 80 75 70 65 60 55 50 45 40 35 30 Paired t-tests: does group 1 change with program Comparison Program Pretest Posttest Paired: does group 2 change Same people over time Ttests Comparison t df p Independent samples t-tests 0.55 Pretest 3.24 Posttest Paired t-tests Control Program 49 49 49 49 .85 .01 .95 .01 0.25 3.33 T-tests Comparison t df p No effects! Independent samples t-tests 0.55 Pretest 3.24 Posttest Paired t-tests Control Program 49 49 49 49 .85 .01 .95 .01 Low t-score High p-value 0.25 3.33 T-tests Comparison t df...
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