Examples of chapter 9.docx - Example 1 Suppose a...

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Example 1 Suppose a sociologist wants to establish that the mean retirement age is greater than 67. It is assumed that retirement age is normally distributed with a known population standard deviation of 9 years (σ = 9). Let a random sample of 25 retirees produce an average retirement age of 71. This sample evidence casts doubt on the validity of the null hypothesis, since the sample mean is greater than the hypothesized value, μ 0 > 67. Perhaps the discrepancy can be explained by pure chance. It is common to evaluate this discrepancy in terms of the appropriate test statistic. Conduct a test at the 5% significance level. Example 2 A research analyst disputes a trade group's prediction that back-to-school spending will average $606.40 per family this year. She believes that average back-to-school spending will significantly differ from this amount. She decides to conduct a test on the basis of a random sample of 30 households with school-

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