Self Check Answers

1. (a) Reasonable populations are all residents in the station’s viewing area or all viewers of the 6 o’clock news. However, certain viewers who feel strongly about this question could call their friends and encourage them to vote even if they are outside of the viewing area. So, it could be all residents in the station’s viewing area and their friends. (There is no clear answer to this question.)

   (b) Sample answer: If the population is all residents in the station’s viewing area, the sample is not representative of the population. For example, people who do not watch the 6 o’clock news will not be represented in this sample. The views of the 6 o’clock news watchers could be quite different from those who do not watch the 6 o’clock news. Also, people who feel strongly about the question are more apt to reply and will thus be overrepresented in the sample.

2. (a) The sample consists of the people who completed the survey and mailed it back to the hospital. This is an example of a voluntary response survey.

   (b) The population is all people having routine medical tests done at this hospital.

   (c) The data will not accurately portray patient satisfaction. Many patients will not bother to fill out the survey, particularly if they did not encounter any problems. People who had a bad experience of some type are probably more likely to complete and mail in the survey.

3. Entering Table 7.1 on line 110, here is a list of two-digit numbers:

   38	44	84	87	89	18	33	82	46	97	39	36	44	20	06	76
   						68	80	87	08

   Since we have not reached a sample of size 5, we move to line 111 and continue the process:

   81

   48

   66

   94

   87

   60

   51

   30

   92

   97

   00

   41

   27

   Our random sample of labels consists of 18, 20, 06, 08, and 27. So, the randomly selected songs will be “All You Need Is Love,” “Lady Madonna,” “A Hard Day’s Night,” “Eight Days a Week,” and “The Long and Winding Road.”

4. Although a few students might refuse to complete the questionnaire, the major problem affecting this survey is undercoverage. The sample will not include students who never eat breakfast or students who were out late Thursday night and didn’t show for Friday breakfast. So, the views of large segments of the student population will not be represented in this survey.
5. Both questions have been designed to elicit particular responses: the first to elicit support for smoking in a hotel room, and the second to obtain support for banning smoking in the workplace. The use of the word freedom in Q1 makes smoking appear as a right and therefore makes it more likely that the respondent will answer “yes.” The introductory phrase in Q2 focuses respondents’ attention on the dangers of smoking and makes it more likely that the respondent will answer “no.”
6. Students who had a class right before their math class might be more tired than those who did not. Because they had back-to-back classes, they might not have had enough time to eat before their math class. Students who did not have a class right before their math class would have had time both to eat and to study for the test before going to math class.
7. This is a retrospective study.

8. (a) In a sample of size 2, it is possible to get 0 “yes” responses, 1 “yes” response, or 2 “yes” responses. Hence, the possible values for would be 0, 0.5, and 1.0.

   (b) Since , it is least likely that both responses are “no.” Hence, will occur least frequently.

9. (a) The distribution is normal and thus it is bell-shaped.

   (b) The mean is 0.7.

   (c) The standard deviation is .

   (d) The distribution is still normal, but its center is shifted to the right compared to the distribution in Example 16. In addition, its standard deviation is slightly smaller.

10. (a)

    (b) The margins of error are close. In fact, if rounded to one decimal place, the margins of error are both 3.1%.