To evaluate the effect of a treatment, a sample of n 5 8 is obtained from a population with a mean of m 5 50, and the treatment is administered to the individuals in the sample. After treatment, the sample mean is found to be M 5 55.

a. Assuming that the sample variance is s 2 5 32, use a two-tailed hypothesis test with a 5 .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 5 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?