Fifty people in the civilian labor force are randomly selected and the sample average age is computed to be 36.4.
(a) Find a 90% confidence interval for the mean age, ?, of all people in the civilian labor force. Assume that the population standard deviation for the ages of civilian labor force is 12.1 years. Interpret the confidence interval.
(b) It is being claimed that the mean age of the population of civilian labor force is 40. What do you conclude based on the confidence interval?