A study compares the effectiveness of a new (Drug A) and an old medicine (Drug B) and finds no difference in effectiveness: t (68) = 1.34, p > .05. The researchers run the study a second time: Both studies are based on the same sample size (Ni= 35), and somehow both studies end up with the same standard deviations for the two groups. However, in the second study, the size of the dosage of Drug A was increased, which increased the difference between the two groups (between-group variability):
a. Calculate the t-test for independent means.
b. What is the effect of increasing between-group variability on the likelihood of rejecting the null hypothesis?
Â c. What is the effect of increasing between-group variability on the likelihood of making a Type II error?