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Sample Size, Confidence Interval

1. The manager of Tee Shirt Emporium reports that the mean number of shirts sold per week is 1210, with a standard deviation of 325. The distribution of sales follows the normal distribution. What is the liklihood of selecting a sample of 25 weeks and finding the sample mean to be 1100 or less?

2. The manager of the local Humberger Express wishes to estimate the mean time customers spend at the drive-through window. A sample of 20 customers experienced a mean waiting time of 2.65 minutes, with a standard deviation of 0.45 minutes. Develop a 90 percent confidence interval for the mean waiting time.

3. In a sample of 200 residents of Georgetown County, 120 reported they believed the county real estate taxes were too high. Develop a 95 percent confidence interval for the proportion of residents who believe the tax rate is too high. Would it be reasonable to conclude that majority of taxpayers feel that the taxes are too high?

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