A random sample of 25 items is drawn from a population whose standard deviation is unknown. The sample mean is x¯ = 850 and the sample standard deviation is s = 15. Use Appendix D to find the values...

A random sample of 25 items is drawn from a population whose standard deviation is unknown. The sample mean is x¯ = 850 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 95 percent confidence.

b. Repeat part a. assuming that s = 30.

c. Repeat part a. assuming that s = 60.

d. Describe how the confidence interval changes as s increases.