8 CHAPTER 1 Introduction to Statistics 38. In January 2021, 54% of the governors of the 50 states in the United States were Republicans. (Source: National Governors Association) 39. In a survey of automobile owners, 6% said they had to change their engine control module at least once. 40. Voter registration records show that 47% of all voters in a county are registered as Democrats. 41. A survey of 1000 U.S. adults found that 79% think that the spread of infectious diseases is a major threat to the well-being of the United States. (Source: Pew Research Center) 42. In a recent year, the average math score on the ACT for all graduates was 20.2. (Source: ACT, Inc.) 43. Descriptive and Inferential Statistics Which part of the survey described in Exercise 31 represents the descriptive branch of statistics? What conclusions might be drawn from the survey using inferential statistics? 44. Descriptive and Inferential Statistics Which part of the survey described in Exercise 32 represents the descriptive branch of statistics? What conclusions might be drawn from the survey using inferential statistics? Extending Concepts 45. Identifying Data Sets in Articles Find an article that describes a survey. (a) Identify the sample used in the survey. (b) What is the population? (c) Make an inference about the population based on the results of the survey. 46. Writing Write an essay about the importance of statistics for one of the following. • A study on the effectiveness of a new drug • An analysis of a manufacturing process • Drawing conclusions about voter opinions using surveys 47. Exercise and Immunity A study showed the same level of T cell production in senior citizens who are amateur cyclists as in young adults, but a significantly lower level of T cell production in senior citizens who do not exercise regularly. Is it appropriate to infer that exercise stimulates T cell production? Explain. (Source: University of Birmingham) 48. Weight Loss and High Blood Pressure A study showed an association between intentional weight loss and a decreased risk of high blood pressure. Is it appropriate to infer from this study that weight loss causes a decreased risk of high blood pressure? Explain. (Source: European Association for the Study of Obesity) 49. Sleep and Student Achievement A study of college students showed that participants earned higher scores on quizzes and midterm exams with better sleep. (Source: The American Journal of Managed Care) (a) Identify the sample used in the study. (b) What is the population? (c) Which part of the study represents the descriptive branch of statistics? (d) Make an inference about the population based on the results of the study.
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