# Statistics in a Modern World 800 Homework 1 NAME:_________________________________

Homework 1 Exercises Assigned from Chapters 1-3 (21 pts.) due Fri. 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 circle YES or NO, then explain briefly.
2.

3. 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 circle YES or NO, then explain briefly.
4.

#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? Circle 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 circle 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.)

#20. (2 pts.) A newspaper headline read "Study finds walking a key to good health: Six brisk outings a month cut death risk." Was this an (a) observational study or (b) experiment? Which of these would be a better headline? (a) "Walking keeps you alive" or (b) "Walkers tend to be healthier" ?

### 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. (1 pt.) 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 of the following Seven Critical Components below (from pp.18-19) would be more relevant in terms of deciding whether to change your coffee-drinking habits? (a) 1, 2, and 5 (b) 3, 4, 6, and 7

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

#11. (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?

#13 (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? (Circle YES or NO.)
2. a reliable measure? (Circle YES or NO.)
[Hint: each year a certain proportion of crimes tend to go unreported.]

#15 (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 question (i) open or (ii) closed?
2. Name an additional choice which definitely should have been included:_____________________________
3. Do the survey results provide good evidence for the advertiser's claim? Circle YES or NO.

#XX (2 pts.)

1. Miles driven using a certain type of gas is what type of variable? (i) discrete measurement (ii) continuous measurement (iii) categorical
2. Type of painkiller used is what type of variable? (i) discrete measurement (ii) continuous measurement (iii) categorical

#18 (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