posted by Melvin .
The general manager for Gordon's Self Service Gasoline is interested in estimating the mean number of gallons of gasoline that are purchased by customers at their Philadelphia location. He would like his estimate to be within plus or minus 0.50 gallons, and he would like the estimate to be at a 99% confidence level. Past studies have shown that the standard deviation for purchase amount is 4.0 gallons. Find the required sample size.
(please provide complete detailed answer)