The Manager of a Grocery Store Has Taken a Random

Multiple Choice

The manager of a grocery store has taken a random sample of 144 customers. The average length of time it took these 144 customers to check out was 3 minutes. It is known that the standard deviation of the population of checkout times is 1 minute. The 95% confidence interval for the true average checkout time (in minutes) is

A) 2.863 to 3.137.
B) 1.36 to 4.64.
C) 1 to 5.
D) 2.837 to 3.163.