An empirical study shows that the cash compensation of corporate chief executive officers (CEOs) of 104 companies increased in 2021. The average increase in compensation is X = 6.9%, and the known population standard deviation () is 5.5%.

a. Construct the 99% confidence interval for . b. Write the null and alternative hypotheses for a test of whether the average compensation of all CEOs increased in 2021.

c. What is the value of your test statistic. Which test statistic did you derive, z or t? Why?

d. Does the study give strong evidence that the average compensation of all CEOs went up? Use = 0.01.