The life in hоurs оf а 75-wаtt light bulb is knоwn to be normаlly distributed with a population standard deviation of 19 hours. This question is part of a quiz or exam given at Arizona State University, copywritten by Dr. L. Chattin. It may not be reproduced, posted or distributed without permission of Arizona State University and L. Chattin. Suppose that we wanted the total width of the two-sided confidence interval to be 7 hours at 95% confidence. What sample size should be used? Round up to the next integer. You must use the online calculator for this problem. Zero credit will be earned if you do not, even if you get the correct answer: ti84calculator.io