chapter_12 - CHAPTER 12 SOLUTIONS AND MINI-PROJECT NOTES...

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CHAPTER 12 SOLUTIONS AND MINI-PROJECT NOTES CHAPTER 12 RELATIONSHIPS BETWEEN CATEGORICAL VARIABLES EXERCISE SOLUTIONS 12.1 No, it is not sufficient. We do not know how many of the men or women were Democrats versus Republicans. 12.2 1.6 per 100,000 is 0.0016% of the population. It is difficult to interpret such a small percentage. The rate of 1.6 per 100,000 is easier to understand. 12.3 The proportion of surgical operations requiring an overnight hospital stay is 0.40; the risk of having to spend the night at the hospital following a surgical procedure is 0.40. The odds of having to spend the night at the hospital versus getting to go home on the same day are 40 to 60, or 4 to 6, or 2 to 3. 12.4 To compute the relative risk use 1/5 divided by 1/50, or 50/5 = 10. Patients who have had heart surgery might be doing themselves a favor by having religious beliefs giving them strength and comfort, or by participating in social activities. An observational study found that patients who had neither of these had a 10 times higher risk of dying within 6 months than patients who had both. 12.5 a. Relative risk = 1 + (increased risk/100) = 1 + 0.25 = 1.25. b. The baseline risk is missing. 12.6 a. Observational study. b. Reasons 3, 4 and 5 are all possibilities. Reason 3 says that firing someone or having a high-stakes deadline may be a contributor to the heart attack. Reason 4 says that there may be confounding variables; in this case, overall job responsibility and consequent stress are likely to be involved. Reason 5, that both having to fire someone (or having a deadline) and having a heart attack result from a common cause is possible; they could both indirectly result from having the type of personality that leads one to be driven to succeed, to take high risks, and so on. c. i. A person who has to fire someone or is subjected to a high-stakes deadline has double the odds of having a heart attack in the following week than someone who has not had to do those things. (Notice that this is not the same thing as saying this person has twice the odds that that same person would have had if they hadn't fired someone or had the deadline.) ii. Although someone who has to fire someone or who has a high-stakes deadline has twice the risk of having a heart attack during the next week as someone who has not done those things, the increased risk is
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This note was uploaded on 10/15/2011 for the course STAT 100 at Penn State.

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chapter_12 - CHAPTER 12 SOLUTIONS AND MINI-PROJECT NOTES...

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