# Statistics in a Modern World 800 Homework 2 NAME:_________________________________

Homework 2 Exercises Assigned from Chapters 4-5 (29 pts.) due Fri. Sept. 18 in Lecture.

### CHAPTER 4

#7 (6 pts.) For each of the following situations, CIRCLE the word or words that tell you what constitutes the POPULATION; UNDERLINE the word or words that tell what constitutes the SAMPLE. Then indicate what type of sample was used.

1. To survey the opinions of its customers, an airline company made a list of all its flights and randomly selected 25 flights. All of the passengers on those flights were asked to fill out a survey.
[Circle one:
1. simple random sample
2. stratified
3. cluster
4. systematic
5. multistage
6. volunteer
7. convenience or haphazard
8. ]
2. A large variety store wanted to know if consumers would be willing to pay slightly higher prices to have computers available throughout the store to help them locate items. The store posted an interviewer at the door and told her to collect a sample of 100 opinions by asking the next person who came in the door each time she had finished an interview. [Circle one: (i) simple random sample (ii) stratified (iii) cluster (iv) systematic (v) multistage (vi) volunteer (vii) convenience or haphazard]

#12 (1 pt.) Which is worse, a volunteer response (low response rate) or a volunteer sample?

#20 (1 pt.) Suppose that a gourmet food magazine wants to know how its readers feel about serving beer with various types of food. The magazine sends surveys to 1000 randomly selected readers. Which one of the "difficulties and disasters" in sampling, p.69, is the magazine most likely to face? (Circle it) 1. Using the wrong sampling frame 2. Not reaching the individuals selected 3. Getting no response or getting a volunteer response 4. Getting a volunteer sample 5. Using a convenience or haphazard sample

### CHAPTER 5

#4 (3 pts.) Refer to Thought Question 5 on p.81. The headline was based on a study in which a representative sample of over 400,000 adults in the U.S. were asked a series of questions, including level of education and on how many of the past 30 days they felt physically and emotionally healthy.

1. For this study, what was the intended explanatory variable---education or health?
2. What was the intended response variable---education or health?

3. Which one of the three "difficulties and disasters in observational studies" p.96 is most worrisome? 1. Confounding variables and the implications of causation 2. Extending the results inappropriately 3. Using the past as a source of data (Circle one.)

#6. (1 pt.) Suppose researchers were interested in determining the relationship, if any, between brain cancer and the use of cellular telephones. Which would be better? (a) an experiment; or (b) a case-control study (Circle one.)

#7. (1 pt.) Researchers have found that women who take oral contraceptives (birth control pills) are at higher risk of having a heart attack or stroke and that the risk is substantially higher if a woman smokes. In investigating the relationship between taking oral contraceptives (the explanatory variable) and having a heart attack or stroke (the response variable), smoking would be called (a) a confounding variable; or (b) an interacting variable (Circle one.)

#12 (3 pts.) Suppose you wanted to know if men or women students spend more money on clothes. You consider two different plans for carrying out an observational study: Plan 1: Ask the participants how much they spent on clothes during the last 3 months; then compare the men and women. Plan 2: Ask the participants to keep a diary in which they record their clothing expenditures for the next 3 months; then compare the men and women.

1. Which of these plans is a retrospective study? Circle one: Plan 1 or Plan 2
2. What term is used for the other plan?
3. Which of the difficulties and disasters p.96 would apply most to Plan 1? Circle it:
1. Confounding variables and the implications of causation
2. Extending the results inappropriately
3. Using the past as a source of data.

#13 (4 pts.) Suppose an observational study finds that people who use public transportation to get to work have better knowledge of current affairs than those who drive to work, but that the relationship is weaker for well-educated people. Label each of the following as being Explanatory, Response, Confounding, or Interacting variable:

1. Method of getting to work ; Circle one: E R C I
2. Knowledge of current affairs; Circle one: E R C I
3. Level of education; Circle one: E R C I
4. Whether the participant reads a daily newspaper; Circle one: E R C I

#15 (6 pts.) A headline in the SACRAMENTO BEE (11 Dec 1997, p.A15) read, "Study: Daily drink cuts death" and the article began with the statement, "One drink a day can be good for health, scientists are reporting, confirming earlier research in a new study that is the largest to date of the effects of alcohol consumption in the U.S." The article also noted that "most subjects were white, middle-class and married, and more likely than the rest of the U.S. population to be college-educated."

1. Explain briefly why this study could not have been an experiment.
2.