Recall that a bank manager has developed a new system to reduce
the time customers spend waiting to be served by tellers during
peak business hours. The mean waiting time during peak business
hours under the current system is roughly 9 to 10 minutes. The bank
manager hopes that the new system will have a mean waiting time
that is less than six minutes. The mean of the sample of 104 bank
customer waiting times is x⎯⎯x¯ = 5.49. If we
let µ denote the mean of all possible bank
customer waiting times using the new system and assume
that σ equals 2.43:
(a) Calculate 95 percent and 99 percent
confidence intervals for µ.
(b) Using the 95 percent confidence
interval, can the bank manager be 95 percent confident
that µ is less than six minutes? Explain.
(c) Using the 99 percent confidence
interval, can the bank manager be 99 percent confident
that µ is less than six minutes? Explain.