posted by Joe .
The mean of a sample of 25 was calculated as xbar = 500. The sample was randomly drawn from a population whose standard deviation is 15. Estimate the population mean with 99% confidence.
B.) Repeat part (a) changing the population standard deviation to 30.
C.) Repeat part (a) changing the population standard deviation to 60.
D.) Describe what happens to the confidence interval estimate when the standard deviation is increased.