The management of the National Private Security Coporation recently conducted a survey of 435 of its employees to determine the average number of hours that each employee sleeps at night. The company statistician submitted the following information to the management: ?x = 1479.8 and ?(x -x-bar )2 = 1755. Where x is the number of hour slept by each employee. Find a 95% confidence interval estimate for the average number of hours that each employee sleeps at night.