measure the size of treatment effect

A random sample is obtained from a population with a mean of μ = 70. A treatment is administered to the individuals in the sample and, after treatment, the sample mean is M = 78 with a standard deviation of s = 20.

a. Assuming that the sample consists of n = 25 scores, compute r2 and the estimated Cohen’s d to measure the size of treatment effect.

b. Assuming that the sample consists of n = 16 scores, compute r2 and the estimated Cohen’s d to measure the size of treatment effect.

c. Comparing your answers from parts a and b, how does the number of scores in the sample influence the measures of effect size?

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