A random sample of 100 items is drawn from a population whose standard deviation is known to

Question:

A random sample of 100 items is drawn from a population whose standard deviation is known to be σ = 50. The sample mean is x-bar = 850.
a. Construct an interval estimate for with 95 percent confidence.
b. Repeat part a assuming that σ = 100.
c. Repeat part a assuming that σ = 200.
d. Describe how the confidence interval changes as increases.