A random sample of 27 items is drawn from a population whose standard deviation is unknown. The sample mean is = 940 and the sample standard deviation is s = 15. Use Appendix D to find the values of Student’s t.

**(a)**Construct an interval estimate of μ with 99% confidence.

**(b)**Construct an interval estimate of μ with 99% confidence, assuming that s = 30.

**(c)**Construct an interval estimate of μ with 99% confidence, assuming that s = 60.

**(d)**Describe how the confidence interval changes as s increases.

The interval stays the same as s increases.

The interval gets wider as s increases.

The interval gets narrower as s increases.