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Intro Stats / AP Statistics
18. To evaluate the effect of a treatment, a sample of n = 8 is obtained from a population with a mean of μ = 50, and the treatment is administered to the individuals in the sample. After treatment, the sample mean is found to be M = 55.
a. Assuming that the sample variance is s^2 = 32, use a two-tailed hypothesis test with α = .05 to determine whether the treatment effect is significant and compute both Cohen's d and r^2 to measure effect size.
b. Assuming that the sample variance is s^2 = 72, repeat the test and compute both measures of effect size.
c. Comparing your answers for parts a and b, how does the variability of the scores in the sample influence the outcome of a hypothesis test and measures of effect size?