Question 1: A psychologist has to develop a new test of spatial perception, and she wants to estimate the mean score achieved by male pilots. How many people must she test if she wants the sample mean to be in error by no more than 2.0 points, with 95% confidence? An earlier study suggests that σ = 21.2.
Question 2: In a study relating the amounts of time required for room service delivery at a newly opened Radisson Hotel, 20 deliveries had a mean time of 24.2 min and a standard deviation of 8.7 min. The sample data appears to have a bell-shaped distribution. Find the 90% confidence interval for the mean time of all deliveries.