PSY 307 – Statistics for the Behavioral SciencesSleep Deprivation ExampleFormat for Data EntryExample (Cont.)SPSS Results (Example)Slide 6Graph of Data (Example)Slide 8SPSS Output for t-TestSlide 10Multiple ComparisonsPSY 307 – Statistics for the Behavioral SciencesChapter 16 – One-Way ANOVA (Cont.)Sleep Deprivation ExampleResearch Problem:On average, are subjects’ aggression scores in a controlled social situation affected by sleep deprivation periods of 0, 24, or 48 hours?State the hypotheses:H0: 0 = 24 = 48H1: H0 is falseFormat for Data Entry1 0.0 0.02 0.0 4.03 0.0 2.04 24.0 3.05 24.0 6.06 24.0 6.07 48.0 6.08 48.0 8.09 48.0 10.0Example (Cont.)Decision Rule:Reject H0 at .05 level of significance if F ≥ 5.14 (from F table), given dfbetween = 2 and dfwithin = 6.Calculations:Use formulas to calculate F(2,6) = 7.36Decision:Reject H0 at the .05 level of significance because 7.36 exceeds 5.14SPSS Results (Example)Example (Cont.)Interpretation of Results:Hours of sleep deprivation do affect the subjects’ mean aggression scores in a controlled social situation.Calculate Effect Size:Divide SSbetween by SStotal to get 2Graph the data to see where the significant group differences are.Graph of Data (Example)Example (Cont.)Perform post-hoc t-tests or planned comparisons to find differences between pairs of means.Hypotheses for Post-Hoc test:H0: 0 – 48 = 0H1: 0 – 48 ≠ 0Decision Rule:Reject H0 at the .05 level of significance if t ≥ 2.78 (from t-table).SPSS Output for t-TestThis is the relevant result.Example (Cont.)Calculations:Use formula for independent samples t-test to calculation t(6) = -3.67.Decision:Reject H0 at the .05 level of significance because -3.67 exceeds -2.78.Interpretation: Sleep deprivation for 48 hrs results in greater aggression.Multiple ComparisonsThe regular t-test assumes that a single comparison is being made.Use of multiple comparisons increases the likelihood of a Type I error.To prevent this, the cumulative probability of all tests is used when determining the critical value for multiple
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