Chapter 10: Problem 40
Step 2 of the five-step process for hypothesis testing is selecting an appropriate method. What is involved in completing this step?
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Chapter 10: Problem 40
Step 2 of the five-step process for hypothesis testing is selecting an appropriate method. What is involved in completing this step?
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"Most Like It Hot" is the title of a press release issued by the Pew Research Center (March 18, 2009, www.pewsocialtrends. org). The press release states that "by an overwhelming margin, Americans want to live in a sunny place." This statement is based on data from a nationally representative sample of 2,260 adult Americans. Of those surveyed, 1,288 indicated that they would prefer to live in a hot climate rather than a cold climate. Suppose that you want to determine if there is convincing evidence that a majority of all adult Americans prefer a hot climate over a cold climate. a. What hypotheses should be tested in order to answer this question? b. The \(P\) -value for this test is 0.000001 . What conclusion would you reach if \(\alpha=0.01 ?\) For questions \(10.85-10.86,\) answer the following four key questions (introduced in Section 7.2 ) and indicate whether the method that you would consider would be a large-sample hypothesis test for a population proportion.
Many people have misconceptions about how profitable small, consistent investments can be. In a survey of 1,010 randomly selected American adults (Associated Press, October 29,1999 ), only 374 responded that they thought that an investment of \(\$ 25\) per week over 40 years with a \(7 \%\) annual return would result in a sum of over \(\$ 100,000\) (the actual amount would be \(\$ 286,640\) ). Is there convincing evidence that less than \(40 \%\) of U.S. adults think that such an investment would result in a sum of over \(\$ 100,000\) ? Test the relevant hypotheses using \(\alpha=0.05\).
Use the definition of the \(P\) -value to explain the following: a. Why \(H_{0}\) would be rejected if \(P\) -value \(=0.0003\) b. Why \(H_{0}\) would not be rejected if \(P\) -value \(=0.350\)
The article "Breast-Feeding Rates Up Early" (USA Today, Sept. 14,2010 ) summarizes a survey of mothers whose babies were born in \(2009 .\) The Center for Disease Control sets goals for the proportion of mothers who will still be breast-feeding their babies at various ages. The goal for 12 months after birth is 0.25 or more. Suppose that the survey used a random sample of 1,200 mothers and that you want to use the survey data to decide if there is evidence that the goal is not being met. Let \(p\) denote the proportion of all mothers of babies born in 2009 who were still breast-feeding at 12 months. (Hint: See Example 10.10 ) a. Describe the shape, center, and spread of the sampling distribution of \(\hat{p}\) for random samples of size 1,200 if the null hypothesis \(H_{0}: p=0.25\) is true. b. Would you be surprised to observe a sample proportion as small as \(\hat{p}=0.24\) for a sample of size 1,200 if the null hypothesis \(H_{0}: p=0.25\) were true? Explain why or why not. c. Would you be surprised to observe a sample proportion as small as \(\hat{p}=0.20\) for a sample of size 1,200 if the null hypothesis \(H_{0}: p=0.25\) were true? Explain why or why not. d. The actual sample proportion observed in the study was \(\hat{p}=0.22 .\) Based on this sample proportion, is there convincing evidence that the goal is not being met, or is the observed sample proportion consistent with what you would expect to see when the null hypothesis is true? Support your answer with a probability calculation.
In a survey of 1,000 women ages 22 to 35 who work full-time, 540 indicated that they would be willing to give up some personal time in order to make more money (USA Today, March 4, 2010). The sample was selected to be representative of women in the targeted age group. a. Do the sample data provide convincing evidence that a majority of women ages 22 to 35 who work fulltime would be willing to give up some personal time for more money? Test the relevant hypotheses using \(\alpha=0.01\) b. Would it be reasonable to generalize the conclusion from Part (a) to all working women? Explain why or why not.
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