Problem 1: 10 points = [3 + 4 + 3] Managers at a service center design studies aimed at estimating the population average time (= /) in minutes spent by customer service representatives per one call. They assume that the individual duration is normally distributed with population standard deviation, o = 12 minutes. 1. Assuming that the margin of error for an interval should not exceed 5 minutes, find the SMALL- EST sample size required for a 99% confidence interval. 2. Determine the SMALLEST sample size needed for the 90% confidence interval that should be NO WIDER than 6 minutes. 3. Determine the width of a 95% interval based on a sample of 100 records. Solution