Statistics in a Modern World 800
Assignment 1

Homework Exercises Assigned from Part 1 (50 pts.) due Wed. Sept. 11 in Lecture

CHAPTER 1

#2. (2 pts.) "People who often attend cultural activities, such as movies, sports events and concerts, are more likely than their less cultured cousins to survive the next eight to nine years, even when education and income are taken into account, according to a survey by the University of Umea in Sweden" (American Health, April 1997, p. 20).

1. Can this claim be tested by conducting an experiment? First answer yes or no, then explain briefly.

 

 

2. On the basis of the study that was conducted, can we conclude that attending cultural events causes people to be likely to live longer? First answer yes or no, then explain briefly.

#5. (2 pts.) "If you have borderline high blood pressure, taking magnesium supplements may help, Japanese researchers report. Blood pressure fell significantly in subjects who got 400-500 milligrams of magnesium a day for four weeks, but not in those getting a placebo" (USA Weekend, 22-24 May 1998, p.11).

1. Do you think this was (i) a randomized experiment or (ii) an observational study?
2. Do you think the relationship found in this study is a causal one, in which taking magnesium actually causes blood pressure to be lowered? Answer yes or no.

#16. (1 pt.) Sometimes television news programs ask viewers to call and register their opinions about an issue. One number is to be called for a "yes" opinion and another number for a "no" vote. Do you think viewers who call are a representative sample of all viewers? First answer yes or no, then explain briefly.

#18(a). (1 pt.) Suppose a researcher would like to determine whether one grade of gasoline produces better gas mileage than another grade. Twenty cars are randomly divided into two groups, with ten cars receiving one grade and ten receiving the other. After many trips, average mileage is computed for each car. In which case would it be easier to detect a difference in gas mileage between the two grades? (i) 20 cars all the same size; or (ii) 20 cars covering a wide range of sizes and weights. (Circle one.)

CHAPTER 2

#9. (3 pts.) Suppose a tobacco company is planning to fund a telephone survey of attitudes about banning smoking in restaurants. In each of the following phases of the survey, should the company disclose who is funding the study? Answer yes or no after each:

1. When respondents answer the phone, before they are interviewed.
2. When the survey results are reported in the news.
3. When the interviewers are trained and told how to conduct the interviews.

#13. (3 pts.) Suppose a study were to find that drinking coffee raised cholesterol levels. Further, suppose you drink two cups of coffee a day and have a family history of heart problems related to high cholesterol. Which three of the Seven Critical Components p.16 should interest you most, in terms of deciding whether to change your coffee-drinking habits? Circle three of these:

1. Source of research and funding
2. Researchers who had contact with participants
3. Individuals studied and how they were selected
4. Exact nature of measurements made or questions asked
5. Setting in which measurements were taken
6. Extraneous differences between groups being compared
7. Magnitude of any claimed effects or differences.

CHAPTER 3

#8. (1 pt.) If we were interested in knowing whether the average price of homes in a certain county had gone up or down this year in comparison with last year, would we be more interested in having a valid measure or a reliable measure?

#10 (2 pts.) To measure the amount of crime in a given city, do you think the crime statistics reported by the police are

1. a valid measure? (Answer yes or no.)
2. a reliable measure? (Answer yes or no.)

#11. (2 pts.) Refer to Case Study 2.1, pp. 26-27, "Brooks Shoes Brings Flawed Study to Court." Circle the two of the seven pitfalls on p. 32 which apply most directly here:

1. Deliberate bias 2. Unintentional bias 3. Desire to please 4. Asking the uninformed

5. Unnecessary complexity 6. Ordering of questions 7. Confidentiality and anonymity

#12 (3 pts.) An advertiser of a certain brand of aspirin (let’s call it Brand B) claims that it is the preferred painkiller for headaches, based on the results of a survey of headache sufferers. The choices given to respondents were: Tylenol, Extra-Strength Tylenol, Brand B Aspirin, Advil.

1. Is this an open- or closed-form question?
2. Name an additional choice which definitely should have been included.
3. Do the survey results provide good evidence for the advertiser's claim? Answer yes or no.

#15 (1 pt.) In February 1998, U.S. president Bill Clinton was under investigation for allegedly having had an extramarital affair. A Gallup Poll asked the following two questions: "Do you think most presidents have or have not had extramarital affairs while they were president?" and then "Would you describe Bill Clinton’s faults as worse than most other presidents, or as no worse than most other presidents?" For the first question, 59% said "have had," 33% said "have not," and the remaining 8% had no opinion. For the second question, 24% said "worse," 75% said "no worse," and only 1% had no opinion. If the first question had NOT been asked before thesecond one, the percentage answering "worse" to the second question would have been (a) lower (b) same (c) higher

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
   ]
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 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.58, 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

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

What was the intended response variable---education or health?

2. Which one of the three "difficulties and disasters in observational studies" p.84 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.84 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. Is the headline justified? Answer yes or no.
3. The study was based on recording drinking habits for the 490,000 participants in 1982, and then noting death rates for the next 9 years. Thus, it was a (i)retrospective (ii)prospective study. (Circle one.)
4. Circle any of the difficulties and disasters in observational studies p.84 that apply (there may be more than one): 1. Confounding variables and the implications of causation. 2. Extending the results inappropriately 3. Using the past as a source of data

#20 (1 pt.) In which of the following is the "experimenter effect" most likely to be present? (circle one): (a) a double-blind experiment (b) a single-blind experiment; or (c) an experiment with no blinding

CHAPTER 4

#17 (2 pts.) Identify each of the following studies as a Survey, Experiment, Observational study, or Case study:

1. A doctor claims to be able to cure migraine headaches. A researcher administers a questionnaire to each of the patients he claims to have cured: Circle one: S E O C
3. A large company wants to compare two incentive plans for increasing sales. The company randomly assigns a number of its sales staff to receive each kind of incentive and compares the average change in sales of the employees under the two plans. Circle one: S E O C

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