I am interested in estimating the mean length of my phone conversations. Suppose that my sample contains 50 phone conversations, my sample mean is 14.5 minutes, and my sample standard deviation is 4.5 minutes. Suppose also that the population of all of ' my phone conversations is sufficiently large that I need not be concerned that I will have a sample containing more than 5% of them.
a) Calculate an 80% confidence interval for the mean length of my phone conversations.
b) Calculate a 95% confidence interval for the mean length of my phone conversations.
c) Calculate a 99% confidence interval for the mean length of my phone conversations.
d) For this question, we will change the values. Suppose my sample mean is 21 minutes and my sample standard deviation is 4 minutes. Calculate a 90% confidence interval for the mean length of my phone conversations.
e) Write a sentence clearly explaining what your answer to 2 d) represents.