Suppose you are planning another experiment like the one in Exercise 9.20.

Based on that data: (1) you are willing to assume that the standard deviation of the difference in means is 1.5°F, and (2) you anticipate that the average temperature in New York tends to be 3°F lower than the corresponding temperature in Washington on the same day.

a. For such a one-sided paired t-test test, how many test days do you need to obtain 95% power at the specified alternative?

b. How many do you need for 99% power?

c. How many do you need for 80% power?