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Incorrect Question 4 0 / 0.5 pts Home Depot wants to know how long the average light bulb lasts. They sample 3,500 families in the United States. Based on past studies the population standard deviation is assumed known to be 400 hours. They want you to develop a 90% condence interval estimate of the mean length of time light bulbs last. You calculate the sample mean to be 1,800 hours. What is the 2 value you should use for the study? -1.64