Chapter 10: Problem 35
Explain when would you use the paired-samples procedure to make confidence intervals and test hypotheses.
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Chapter 10: Problem 35
Explain when would you use the paired-samples procedure to make confidence intervals and test hypotheses.
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In a random sample of 800 men aged 25 to 35 years, \(24 \%\) said they live with one or both parents. In another sample of 850 women of the same age group, \(18 \%\) said that they live with one or both parents. a. Construct a \(95 \%\) confidence interval for the difference between the proportions of all men and all women aged 25 to 35 years who live with one or both parents. b. Test at a \(2 \%\) significance level whether the two population proportions are different. c. Repeat the test of part b using the \(p\) -value approach.
The following information was obtained from two independent samples selected from two populations with unequal and unknown population standard deviations. $$ \begin{array}{lll} n_{1}=48 & \bar{x}_{1}=.863 & s_{1}=.176 \\ n_{2}=46 & \bar{x}_{2}=.796 & s_{2}=.068 \end{array} $$ Test at a \(1 \%\) significance level if the two population means are different.
When are the samples considered large enough for the sampling distribution of the difference between two sample proportions to be (approximately) normal?
Assuming that the two populations have unequal and unknown population standard deviations, construct a \(99 \%\) confidence interval for \(\mu_{1}-\mu_{2}\) for the following. $$ \begin{array}{lll} n_{1}=48 & \bar{x}_{1}=.863 & s_{1}=.176 \\ n_{2}=46 & \bar{x}_{2}=.796 & s_{2}=.068 \end{array} $$
A car magazine is comparing the total repair costs incurred during the first three years on two sports cars, the T-999 and the XPY. Random samples of 45 T-999s and 51 XPYs are taken. All 96 cars are 3 years old and have similar mileages. The mean of repair costs for the 45 T-999 cars is \(\$ 3300\) for the first 3 years. For the 51 XPY cars, this mean is \(\$ 3850\). Assume that the standard deviations for the two populations are \(\$ 800\) and \(\$ 1000\), respectively. a. Construct a 99\% confidence interval for the difference between the two population means. b. Using a \(1 \%\) significance level, can you conclude that such mean repair costs are different for these two types of cars? c. What would your decision be in part b if the probability of making a Type I error were zero? Explain.
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