Page 575, #12: Race and smoking 2005. In 2005 the New Jersey Adult Tobacco Survey found that \(22.5 \%\) of 464 blacks surveyed said that they smoked cigarettes while \(18.3 \%\) of 2449 white respondents reported smoking.

1. Create a \(90 \%\) confidence interval for the difference in the percentage of smokers between black and white adults in New Jersey.
2. Does this survey indicate a race-based difference in smoking among American adults? Explain, using your confidence interval to test an appropriate hypothesis.
3. What alpha level did your test use?

Page 576, #20: Depression. A study published in the Archives of General Psychiatry in March 2001 examined the impact of depression on a patient's ability to survive cardiac disease. Researchers identified 450 people with cardiac disease, evaluated them for depression, and followed the group for 4 years. Of the 361 patients with no depression, 67 died. Of the 89 patients with minor or major depression, 26 died. Among people who suffer from cardiac disease, are depressed patients more likely to die than nondepressed ones?

1. What kind of design was used to collect these data?
2. Write appropriate hypotheses.
3. Are the assumptions and conditions necessary for inference satisfied?
4. Test the hypothesis and state your conclusion.
5. Explain in this context what your P-value means.
6. If your conclusion is actually incorrect, which type of error did you commit?

Page 576, #22: Depression revisited. Consider again the study of the association between depression and cardiac disease survivability in Exercise 20 .

1. Create a \(95 \%\) confidence interval for the difference in survival rates.
2. Interpret your interval in this context.
3. Carefully explain what " \(95 \%\) confidence" means.

Page 612, #22: Late arrivals. Will your flight get you to your destination on time? The U.S. Bureau of Transportation Statistics reported the percentage of flights that were late each month from 1995 through 2006 . Here's a histogram, along with some summary statistics:

We can consider these data to be a representative sample of all months. There is no evidence of a time trend \((r=-0.07)\)

1. Check the assumptions and conditions for inference about the mean.
2. Find a \(99 \%\) confidence interval for the true percentage of flights that arrive late.
3. Interpret this interval for a traveler planning to fly.

Page 613, #28: Catheters. During an angiogram, heart problems can be examined via a small tube (a catheter) threaded into the heart from a vein in the patient's leg. It's important that the company that manufactures the catheter maintain a diameter of \(2.00 \mathrm{~mm}\). (The standard deviation is quite small.) Each day, quality control personnel make several measurements to test \(\mathrm{H}_{0}: \mu=2.00\) against \(\mathrm{H}_{\mathrm{A}}: \mu \neq 2.00\) at a significance level of \(\alpha=0.05\). If they discover a problem, they will stop the manufacturing process until it is corrected.

1. Is this a one-sided or two-sided test? In the context of the problem, why do you think this is important?
2. Explain in this context what happens if the quality control people commit a Type I error.
3. Explain in this context what happens if the quality control people commit a Type II error.

Page 613, #34:

Doritos. Some students checked 6 bags of Doritos marked with a net weight of 28.3 grams. They carefully weighed the contents of each bag, recording the following weights (in grams): 29.2,28.5,28.7,28.9,29.1,29.5.

1. Do these data satisfy the assumptions for inference? Explain.
2. Find the mean and standard deviation of the observed weights.
3. Create a \(95 \%\) confidence interval for the mean weight of such bags of chips.
4. Explain in context what your interval means.
5. Comment on the company's stated net weight of 28.3 grams.

Page 614 #38: Portable phones. A manufacturer claims that a new design for a portable phone has increased the range to 150 feet, allowing many customers to use the phone throughout their homes and yards. An independent testing laboratory found that a random sample of 44 of these phones worked over an average distance of 142 feet, with a standard deviation of 12 feet. Is there evidence that the manufacturer's claim is false?

Page 614, #40: Yogurt. Consumer Reports tested 14 brands of vanilla yogurt and found the following numbers of calories per serving:

160 200 220 230 120 180 140

130 170 190 80 120 100 170

1. Check the assumptions and conditions for inference.
2. Create a \(95 \%\) confidence interval for the average calorie content of vanilla yogurt.
3. A diet guide claims that you will get 120 calories from a serving of vanilla yogurt. What does this evidence indicate? Use your confidence interval to test an appropriate hypothesis and state your conclusion.

Page 614, #44: Wind power. Should you generate electricity with your own personal wind turbine? That depends on whether you have enough wind on your site. To produce enough energy, your site should have an annual average wind speed of at least 8 miles per hour, according to the Wind Energy Association. One candidate site was monitored for a year, with wind speeds recorded every 6 hours. A total of 1114 readings of wind speed averaged \(8.019 \mathrm{mph}\) with a standard deviation of \(3.813 \mathrm{mph}\). You've been asked to make a statistical report to help the landowner decide whether to place a wind turbine at this site.

1. Discuss the assumptions and conditions for using Student's \(t\) inference methods with these data. Here are some plots that may help you decide whether the methods can be used:
   
   
   
2. What would you tell the landowner about whether this site is suitable for a small wind turbine? Explain.

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