SUPPLEMENTARY EXERCISES for ... - WH Freeman

Section 1 21American farms. The variable is an “index number” that gives productivity as a percent of the1967 level.Year 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990Productivity 21 27 35 47 67 91 113 137 166 217 230Plot these data and also plot the logarithms of the productivity values against year. Then brieflydescribe the pattern of growth that your plots suggest.Chapter 3Section 1S3.1 A letter to the editor of Organic Gardening magazine (August 1980) said, “Today I noticedabout eight stinkbugs on the sunflower stalks. Immediately I checked my okra, for I was surethat they’d be under attack. There wasn’t one stinkbug on them. I’d never read that stinkbugsare attracted to sunflowers, but I’ll surely interplant them with my okra from now on.”Explain briefly why this anecdote does not provide good evidence that sunflowers attractstinkbugs away from okra. In your explanation, suggest some factors that might account for allof the bugs being on the sunflowers.S3.2 There may be a “gender gap” in political party preference in the United States, withwomen more likely than men to prefer Democratic candidates. A political scientist selects alarge sample of registered voters, both men and women. She asks every voter whether theyvoted for the Democratic or the Republican candidate in the last congressional election. Isthis an observational study or an experiment? Why? What are the explanatory and responsevariables?S3.3 What is the preferred treatment for breast cancer that is detected in its early stages?The most common treatment was once mastectomy (removal of the breast). It is now usualto remove the tumor and nearby lymph nodes, followed by radiation. To study whether thesetreatments differ in their effectiveness, a medical team examines the records of 25 large hospitalsand compares the survival times after surgery of all women who have had either treatment.(a) What are the explanatory and response variables?(b) Explain carefully why this study is not an experiment.(c) Do you think this study will show whether a mastectomy causes longer average survivaltime? Explain your answer carefully.S3.4 A study of the effect of living in public housing on family stability and other variablesin poverty-level households was carried out as follows. The researchers obtained a list of allapplicants for public housing during the previous year. Some applicants had been accepted,while others had been turned down by the housing authority. Both groups were interviewed andcompared. Was this study an experiment? Why or why not? What are the explanatory andresponse variables in the study?