a. After sampling 1,000 members of a normal population, you find x = 15,500 and s = 9,950. Estimate the population mean with 90% confidence. b. Repeat part (a) assuming that you know that the...

a. After sampling 1,000 members of a normal population, you find x = 15,500 and s = 9,950. Estimate the population mean with 90% confidence. b. Repeat part (a) assuming that you know that the population standard deviation is σ = 9,950. c. Explain why the interval estimates were virtually identical.