Joes Trucking provides shipping service from the outlying areas of New York City to a

Joes Trucking provides shipping service from the outlying areas of New York City to a known distribution point within Manhattan. To understand the number of trucks required for a given service level agreement defined by a guaranteed delivery interval, the operations manager conducts a study of drive times. The manager would like to obtain an accuracy of 10 min, plus or minus 5 minutes.

Randomly sampling the drive times over a 30-day period, including weekends and all times of day, produces 300 data points. A 95 percent confidence interval is required to ensure customer satisfaction. The mean is found to be 3.01 hours, with a standard deviation of 0.64.

Is the sample size adequate for the accuracy requirements? If yes, determine the confidence interval for the mean delivery time.