Chapter 5 - Chapter 5 5.1 In an observational study, there...

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Chapter 5 5.1 In an observational study, there is no attempt to control factors that might influence the variable of interest. In an experimental study, a factor (such as regular use of a fitness center) is controlled by randomly selecting who is exposed to that factor, thereby reducing the influence of other factors on the variable of interest. 5.2a The study is observational. The statistics practitioner did not randomly assign stores to buy cans or bottles. b Randomly assign some stores to receive only cans and others to receive only bottles. 5.3 Randomly sample smokers and nonsmokers and compute the proportion of each group that has lung cancer. b The study is observational. Experimental data would require the statistics practitioner to randomly assign some people to smoke and others not to smoke. 5.4a A survey can be conducted by means of a personal interview, a telephone interview, or a self- administered questionnaire. b A personal interview has a high response rate relative to other survey methods, but is expensive because of the need to hire well-trained interviewers and possibly pay travel-related costs if the survey is conducted over a large geographical area. A personal interview also will likely result in fewer incorrect responses that arise when respondents misunderstand some questions. A telephone interview is less expensive, but will likely result in a lower response rate. A self-administered questionnaire is least expensive, but suffers from lower response rates and accuracy than interviews. 5.5 Five important points to consider when designing a questionnaire are as follows: (1) The questionnaire should be short. (2) Questions should be short, clearly worded, and unambiguous. (3) Consider using dichotomous or multiple-choice questions, but take care that respondents needn’t make
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Chapter 5 - Chapter 5 5.1 In an observational study, there...

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