A sample of n = 40 is selected from a normal population with = 75 msec.

Question:

A sample of n = 40 is selected from a normal population with µ = 75 msec. and s = 12, and a treatment is administered to the sample. The treatment is expected to increase scores by an average of 4 msec.
a. If the treatment effect is evaluated with a twotailed hypothesis test using a = .05, what is the power of the test?
b. What is the power of the test if the researcher uses a one-tailed test with a = .05?