A) What is the critical value of z for a 99% confidence interval
for a known standard deviation?
B) A 99% confidence interval for the mean of a population
was found to be (123.33, 140.67). If the sample size was 40,
find the margin of error for this estimation.
C) A 95% confidence interval for a population mean is
(12.9, 18.6). Which of the following is the sample mean used
to calculate this interval?