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STA 2023, Spring 2005, Sample 9 Round all answers to three decimal places unless otherwise indicated. 1. A 99% confidence interval is to be determined for a population mean based on a sample of size 28, with the population standard deviation unknown. What is the appropriate critical value tα/2? _____2.771______ A simple random sample of 30 actuaries is selected, and a WAIS-III IQ test is administered to each. The sample mean IQ score is 110.5. Assume that scores on this IQ test for actuaries are normally distributed, and have a population standard deviation of 20 points. 2. Compute the standard error of the sample mean. _____3.652______ 3. Determine a 99% confidence interval for the population mean. Express as an interval, with an upper and a lower bound. _(101.096, 119.904)_ 4. For a 99% confidence interval for the population mean were to have a margin of error of exactly 1.5 IQ points, what sample size would be needed? (round appropriately) ____1179______ For a simple random sample of 19 adult males, the sample mean systolic blood pressure (SBP) is 119.8, with a sample standard deviation of 12.5. Assume that the SBP of adult males follows a normal distribution. 5. What is the margin of error for a 90% confidence interval for the population mean SBP? ____4.973______ 6. What is the margin of error for a 95% confidence interval for the population mean SBP? ____6.025______