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Power and Effect Size

Power and Effect Size. I factor 4 levels. Testing?. effect. TREATMENT. NULL. power. β. 1 - β. 1- α. α /2. α /2. What determines power? Effect size Sample size Variability Significance level 1 or 2 tail choice Kind of test. effect. NULL. TREATMENT. power. β. 1 - β. 1- α.

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Power and Effect Size

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  1. Power and Effect Size

  2. I factor 4 levels

  3. Testing?

  4. effect TREATMENT NULL power β 1 - β 1- α α/2 α/2

  5. What determines power? • Effect size • Sample size • Variability • Significance level • 1 or 2 tail choice • Kind of test

  6. effect NULL TREATMENT power β 1 - β 1- α α/2 α/2

  7. Change significance level

  8. 1 or 2 tail

  9. power is in the sampling distributions, whereas effect size is in the population distributions

  10. assumptions

  11. Effect Size The extent to which 2 populations do not overlap d =( μ1 - μ2)/ σ Cohen’s d 0.2 is small effect 0.5 medium 0.8 large

  12. Approximate number of participants in each group (equal variances) to achieve 80% power for one-way ANOVA at 0.05 significance level How many?

  13. Degrees of freedom 2 factor Factor A has a levels and df= a-1 Factor B has b levels and df = b-1 Interaction df = (a-1)(b-1) Error df = N - ab

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