A random sample of n = 16 scores is obtained from a population with a mean of µ = 45. After a treatment is administered to the individuals in the sample, the sample mean is found to be µ = 49.2.
a. Assuming that the sample standard deviation is s = 8, compute r2 and the estimated Cohen's d to measure the size of the treatment effect.
b. Assuming that the sample standard deviation is s = 20, compute r2 and the estimated Cohen's d to measure the size of the treatment effect.
c. Comparing your answers from parts a and b, how does the variability of the scores in the sample influence the measures of effect size?