A large body of literature on the effect of peer pressure has shown that the mean influence score for a scale of peer pressure is 520 with a standard deviation of 80. An investigator would like to show that a minor change in conditions will produce scores with a mean of only 500, and he plans to run a t test to compare his sample mean with a population mean of 520.

1.What is the effect size in question?

2. What is the power of the test

b)

A second investigator thinks that she can show that a quite different manipulation can raise the mean influence score from 520 to 550.

1.What is the effect size in question?

What is the power of the test?