To evaluate the effect of a treatment, a sample is obtained from a population with a mean of m 5 20, and the treatment is administered to the individuals in the sample. After treatment, the sample mean is found to be M 5 21.3 with a variance of s 2 5 9.

a. Assuming that the sample consists of n 5 16 individuals, 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. Are the data sufficient to conclude that the treatment has a significant effect using a two-tailed test with a 5 .05?

b. Assuming that the sample consists of n 5 36 individuals, repeat the test and compute both measures of effect size.

c. Comparing your answers for parts a and

b, how does the size of the sample influence the outcome of a hypothesis test and measures of effect size?