Question
1. Athletes' salaries. Here is a small part of a data set that describes Major League Baseball players as of opening day of the 2011
1. Athletes' salaries. Here is a small part of a data set that describes Major League Baseball players as of opening day of the 2011 season:
(a) What individuals does this data set describe?
(b) In addition to the player's name, how many variables does the data set contain? Which of these variables take numerical values?Which of the variables are not numerical variables?
(c) What do you think are the units in which each of the numerical variable salary is expressed? For example, what does itmean to give Josh Beckett's annual salary as 17,000? (Hint: The average annual salary of a Major League Baseball player on opening day, 2011, was $3,305,393.)
2. Sampling moms. Pregnant and breast-feeding women should eat at least 12 ounces of fish and seafood per week to ensure their babies' optimal brain development, according to a coalition of top scientists from private groups and federal agencies. A nutritionist wants to know whether pregnant women are eating at least 12 ounces of fish per week. To do so, she obtains a list of the 340 members of a local chain of prenatal fitness clubs and mails a questionnaire to 60 of these women selected at random. Only 21 questionnaires are returned.
(a)What is the variable measured in this study?
(b)What is the population in this study?
(c)What is the sample from which information is actually obtained?
(d)What percentage of the women whom the nutritionist tried to contact responded?
(e)Is this an observational study or an experiment?
3. Oatmeal and cholesterol. Does eating oatmeal reduce the level of bad cholesterol (LDL)? Here are two ways to study this question.
1. A researcher finds 500 adults over 40 who regularly eat oatmeal or products made from oatmeal. She matches each with a similar adult who does not regularly eat oatmeal or products made from oatmeal. She measures the bad cholesterol (LDL) for each adult and compares both groups.
2. Another researcher finds 1000 adults over 40 who do not regularly eat oatmeal or products made from oatmeal and are willing to participate in a study. She randomly assigns 500 of these to a diet that includes a daily breakfast of oatmeal. The other 500 continue their usual habits. After 6 months, she compares changes in LDL levels.
(a) One of these studies is an observational study and the other is an experiment.Identify with study it the experiment and which study is the observational study and explain why for each.
(b) Why does the experiment give more useful information about whether oatmeal reduces LDL?
4. Choose your study type. What is the best way to answer each of the questions below: an experiment, a sample survey, or an observational study that is not a sample survey? Explain your choices.
(a) Is your school's basketball team called for fewer fouls in home games than in away games?
(b) Are college students satisfied with the quality of recreational facilities available to them?
(c) Do college students who have access to audio recordings of course lectures perform better in the course than those who don't?
5. Choose your study purpose. Give an example of a question about college students, their behavior, or their opinions that would best be answered by
(a) a sample survey.
(b) an observational study that is not a sample survey.
(c) an experiment.
6. Definitions.What is the difference between a census and a sample survey?
7. Instant opinion. On March 29, 2007, BusinessWeek ran an online poll on their Web site and asked readers the question "Do you think Google is too powerful?" Readers clicked on one of three buttons ("Yes," "No," or "Not sure") to vote. In all, 1336 (35.9%) said "Yes," 2051 (55.1%) said "No," and 335 (9.0%) said "Not sure."
(a) What is the sample size for this poll?
(b) At the Web site, BusinessWeek includes the following statement about its online poll. "Note: These are surveys, not scientific polls." Explain why the poll may give unreliable information.
(c) Just above the poll question was the following statement: "Google's accelerating lead in search and its moves into software and traditional advertising are sparking a backlash among rivals." How might this statement affect the poll results?
8. Ann Landers takes a sample. Advice columnist Ann Landers once asked her divorced readers whether they regretted their decision to divorce. She received approximately 30,000 responses, about 23,000 of which came from women. Nearly 75% said they were glad they divorced, and most of them said they wished they had done it sooner. Explain why this sample is certainly biased. What is the likely direction of the bias? That is, is 75% probably higher or lower than the truth about the population of all adults who have been divorced?
9. A call-in opinion poll. In 2005 the San Francisco Bay Times reported on a poll in New Zealand that found that New Zealanders opposed the nation's new gay-inclusive civil-unions law by a 3-1 ratio. This poll was a call-in poll that cost $1 to participate in. The San Francisco Bay Times article also reported that a scientific polling organization found that New Zealanders favor the law by a margin of 56.4% to 39.3%. Explain to someone who knows no statistics why the two polls can give such widely differing results and which poll is likely to be more reliable.
10. Choose an SRS. A firm wants to understand the attitudes of its minority managers toward its system for assessing management performance. Below is a list of all the firm's managers who are members of minority groups. Use TableA at line 134 to choose 6 to be interviewed in detail about the performance appraisal system.
01
Berliner
09
Hans
17
Liu
25
Rumsey
02
Browne
10
Herbei
18
MacEachern
26
Shantner
03
Calder
11
Holloman
19
Niller
27
Shi
04
Craigmile
12
Hsu
20
Nagaraja
28
Stasny
05
Cressie
13
Kaizar
21
Notz
29
Turkmen
06
Critchlow
14
Kubatko
22
Ozturk
30
Verducci
07
Dean
15
Lee
23
Pearl
31
Wolfe
08
Goel
16
Lin
24
Peruggia
32
Xu
11. An election day sample. You want to choose an SRS of 20 of a city's 480 voting precincts for special voting-fraud surveillance on election day.
(a) Explain clearly how you would label the 480 precincts. How many digits make up each of your labels? What is the greatest number of precincts you could label using this number of digits?
(b) Use TableA to choose the SRS, and list the labels of the precincts you selected. Enter TableA at line 107.
12. Apartment living. You are planning a report on apartment living in a college town. You decide to select three apartment complexes at random for in-depth interviews with residents. Use TableA, starting at line 121, to select a simple random sample of three of the following apartment complexes.
01
Albany Commons
13
Gaslight Village
25
Oak Run
02
Apple Run
14
Georgetowne
26
Old Nantucket
03
Bexley Court
15
Golf Pointe
27
Parliament Ridge
04
Brooks Edge
16
Hickory Mill
28
Pheasant Run
05
Canterbury Way
17
Highview Place
29
Ravine Bluff
06
Chablis Villas
18
Indian Creek
30
Rocky Creek
07
Cherryblossom Way
19
Jefferson Commons
31
Scioto Commons
08
Dublin Plaza
20
Kenbrook Village
32
Stratford East
09
English Village
21
Lawn Manor
33
Timbercreek
10
Fairway Lakes
22
Little Brook Place
34
Walnut Knolls
11
Forest Creek
23
Marble Cliff
35
Woodland Trace
12
Forest Park
24
Morse Glen
36
York Terrace
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