A Random Sample Of 27 Items Is Drawn From A Population Whose Standard Deviation

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.

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