A speedy oil and lubrication chain surveyed its stores as to the time needed to process a customer. Six customers from each of its 17 stores were selected at random and monitored. The processing times...

A speedy oil and lubrication chain surveyed its stores as to the time needed to process a customer. Six customers from each of its 17 stores were selected at random and monitored.  The processing times had a mean of 11 minutes with a standard deviation of 5.8 minutes.  Find a 95% CI for the mean time needed to process a custome