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QUESTION 21 A sales manager for an automobile parts retail store wanted to estimate the commission that could be expected from the following data. 2,200 2,500 2,400 1,600 1,500 2,000 2,100 2,300 The manager wanted to be 90% confident that the true mean was found Upper Confidence Limit = ? QUESTION 22 A random sample of university students was surveyed to determine the amount of time spent weekly using a personal computer. The times are shown below. If the times are normally distributed with a population variance of 9 hours, estimate with 90% confidence the mean weekly time spent using a personal computer by all university students. The manager wanted to be 90% confident that the true mean was found st a = ? QUESTION 23 A random sample of university students was surveyed to determine the amount of time spent weekly using a personal computer. The times are shown below. If the times are normally distributed with a population variance of 9 hours, estimate with 90% confidence the mean weekly time spent using a personal computer by all university students. The manager wanted to be 90% confident that the true mean was found. Standard Deviation = ? (4 Decimal)