A study was conducted to examine the possible relationship between coronary disease

is effective because the students using the software had significantly higher scores on the SAT than did the students who did not use the software. 2.3 A news report states that minority children who take advanced mathematics courses in high school have a first-year GPA in college that is equivalent to white students. The newspaper columnist suggested that the lack of advanced mathematics courses in high school curriculums in inner city schools was a major cause of inner city schools having a low success rate in college. What confounding variables may be present that invalidate the columnist’s conclusion? 2.4 A study was conducted to determine if the inclusion of a foreign language requirement in high schools may have a positive effect on a students’ performance on standardized English exams. From a sample of 100 high schools, 50 of which had a foreign language requirement and 50 that did not, it was found that the average score on the English proficiency exam was 25 higher for the students having a foreign language requirement. What confounding variables may be present that would invalidate the conclusion that requiring a foreign language in high school increases English language proficiency? 2.3 Sampling Designs for Surveys Soc. 2.5 An experimenter wants to estimate the average water consumption per family in a city. Discuss the relative merits of choosing individual families, dwelling units single-family houses, apartment buildings, etc., and city blocks as sampling units. H.R. 2.6 An industry consists of many small plants located throughout the United States. An execu- tive wants to survey the opinions of employees on the industry vacation policy. What would you suggest she sample? Pol. Sci. 2.7 A political scientist wants to estimate the proportion of adult residents of a state who favor a unicameral legislature. What could be sampled? Also, discuss the relative merits of personal interviews, telephone interviews, and mailed questionnaires as methods of data collection. Bus. 2.8 Two surveys were conducted to measure the effectiveness of an advertising campaign for a low-fat brand of peanut butter. In one of the surveys, the interviewers visited the home and asked whether the low-fat brand was purchased. In the other survey, the interviewers asked the person to show them the peanut butter container when the interviewee stated he or she had purchased low-fat peanut butter.

a. Do you think the two types of surveys will yield similar results on the percentage of

households using the product? b. What types of biases may be introduced into each of the surveys? Edu. 2.9 Time magazine, in an article in the late 1950s, stated that “the average Yaleman, class of 1924, makes 25,111 a year,” which, in today’s dollars, would be over 150,000. Time’s estimate was based on replies to a sample survey questionnaire mailed to those members of the Yale class of 1924 whose addresses were on file with the Yale administration in the late 1950s. a. What is the survey’s population of interest? b. Were the techniques used in selecting the sample likely to produce a sample that was representative of the population of interest? c. What are the possible sources of bias in the procedures used to obtain the sample? d. Based on the sources of bias, do you believe that Time’s estimate of the salary of a 1924 Yale graduate in the late 1950s is too high, too low, or nearly the correct value? 2.10 The New York City school district is planning a survey of 1,000 of its 250,000 parents or guardians who have students currently enrolled. They want to assess the parents’ opinion about mandatory drug testing of all students participating in any extracurricular activities, not just sports. An alphabetical listing of all parents or guardians is available for selecting the sample. In each of the following descriptions of the method of selecting the 1,000 participants in the survey, identify the type of sampling method used simple random sampling, stratified sampling, or clus- ter sampling.

a. Each name is randomly assigned a number. The names with numbers 1 through 1,000

are selected for the survey.