A random sample of 21 items is drawn from a population whose standard deviation is unknown. The sample mean is x¯ = 750 and the sample standard deviation is s = 10. Use Appendix D to find the values of Student’s t. (a) Construct an interval estimate of μ with 98% confidence. (Round your answers to 3 decimal places.) The 98% confidence interval is from (b) Construct an interval estimate of μ with 98% confidence, assuming that s = 20. (Round your answers to 3 decimal places.) The 98% confidence interval is from
to

(c) Construct an interval estimate of μ with 98% confidence, assuming that s = 40. (Round your answers to 3 decimal places.)

The 98% confidence interval is from
to

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