The amount of time a bank teller spends with each customer has a population mean of LI = 3.10 minutes and a standard deviation of a = 0.40 minute. If you select a random sample of 16 customers,
a. What is the probability that the mean time spent per customer is at least 3 minutes?
b. There is an 85% chance that the sample mean is less than how many minutes?
c. What assumption must you make in order to solve (a) and (b)?
d. If you select a random sample of 64 customers, there is an 85% chance that the sample mean is less than how many minutes?