Suppose the times of delivery from an area distributor are normally distributed If the population standard deviation is 2 hours what minimum sample size is needed to be 90 confident that the sample mean is within 1 hour of the true population mean 20 10 20 05 20 025 20 01 20 005 1 282 1 645 1 960 2 326 2 576 Use the table above for the 2 score Round only at the final step Provide your answer below