Question 1

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 According to a CNN poll released in January of 2010, 56 percent of the public opposed the stimulus bill, with 42 percent supportive of the plan. The CNN/Opinion Research Corporation poll was conducted January 8-10, with 1,021 adult Americans questioned by telephone. The survey's sampling error was reported as plus or minus 3 percentage points.
-What is the approximate margin of error for this survey? Did the story report the correct margin of error?

Accepted Answer

The answer of Use the following information for questions:
 According...

Question 2

A random sample of 1,002 adults aged at least 18 years and living in the 48 contiguous states (i.e. any state in the United States excluding Alaska and Hawaii) was conducted by the Gallup Organization. The interviews were done over the telephone. The population represented by this sample was

Accepted Answer

A)  all adult Americans in the 48 contiguous states living in a household with a phone. 
B)  all adult Americans living in the same cities as people who were actually sampled. 
C)  all adult Americans. 
D)  all Americans.

Question 3

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 In a study of patients who had a heart attack, 3630 patients were randomly assigned to receive one of three treatments: aspirin alone, warfarin alone, or aspirin plus warfarin. The results showed that 20.0% of the aspirin group had another heart attack, stroke, or died, compared with 16.7% of the warfarin group and 15.0% of the aspirin plus warfarin group. The difference between the aspirin and warfarin groups was statistically significant, while the difference between the warfarin and aspirin plus warfarin group was not statistically significant.
-The non-statistically significant difference between the warfarin alone group (16.7%) and the aspirin plus warfarin group (15.0%) means that

Accepted Answer

A)  the difference between the two rates, 16.7% and 15.0%, is not medically important. 
B)  the difference between the two rates, 16.7% and 15.0%, is medically important. 
C)  the difference between the two rates, 16.7% and 15.0%, is unlikely to have resulted from two groups whose true rates were identical. 
D)  the difference between the two rates, 16.7% and 15.0%, may have occurred by chance between two groups whose true rates were identical.

Question 4

Suppose that a survey of 20,000 high school students (10,000 girls and 10,000 boys) was done. Students were asked if they had used cocaine during the last 30 days. 4.9% of the boys and 4.2% of the girls reported using cocaine. The difference between the two percentages is statistically significant. Explain why this difference may not be practically significant.

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The answer of Suppose that a survey of 20,000 high...

Question 5

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 Suppose you were to read about a study showing that people who sleep less than five hours a night have twice as much risk of a premature death as people who sleep seven or eight hours a night.
-The "baseline risk"in this context is

Accepted Answer

A)  the risk of premature death for people who sleep less than five hours a night. 
B)  the risk of premature death for people who sleep seven or eight hours a night. 
C)  the risk of premature death for all people. 
D)  the risk of premature death at the beginning of the study for those in the study.

Question 6

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 A five number summary for hours studied in a week were 5, 12, 14, 18, and 20.
-What is the value such that 75% or more of the students studied longer than that value?

Accepted Answer

A)  5 hours 
B)  12 hours 
C)  14 hours 
D)  18 hours

Question 7

A survey of people applying for a mortgage showed that among white people with a bad credit rating, 90% were approved for mortgages, whereas among black people with a bad credit rating, 81% were approved. What confounding variable could also explain the apparent racial difference in the percentage of approved mortgages?

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The answer of A survey of people applying for a...

Question 8

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 In a 1994 Census Bureau report, the total number of households and the number of households with a married couple and their own children were reported for the years 1990 and for 1994. The results are given below:
  One newspaper reported these results with the following headline: "Number of Two-Parent Families Up." Another newspaper, based on the percentages, reported on the same results with the headline: "Traditional Families Less Common".
-In 1990, what percentage of households consisted of a married couple with children?

Accepted Answer

The answer of Use the following information for questions:
 In...

Question 9

An Islamic survey conducted by the Gallup organization consisted of a random sample of 10,004 people living in 9 predominantly Islamic countries. Calculate the approximate margin of error for the survey.

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The answer of An Islamic survey conducted by the Gallup...

Question 10

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 Suppose you were to read about a study showing that people who sleep less than five hours a night have twice as much risk of a premature death as people who sleep seven or eight hours a night.
-Which of the following is not an example of a possible "confounding variable"in this study?

Accepted Answer

A)  Medications a person is taking. 
B)  The amount of alcohol a person drinks in the evening. 
C)  The amount of stress a person is under in their work. 
D)  The amount of sleep a person gets per night.

Question 11

One of the common elements of the eight case studies in Chapter 1 is

Accepted Answer

A)  in each case, a randomized experiment is described. 
B)  in each case, an observational study is described. 
C)  in each case, confounding variables are a problem. 
D)  in each case, data are used to make a judgment about the situation.

Question 12

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 First-year college students' self-ratings of their emotional health dropped to record low levels in 2010, according to the CIRP Freshman Survey, UCLA's annual survey of the nation's entering students at four-year colleges and universities. The rate of students who reported that their emotional health was in the "highest 10 percent" or "above average" was 519 per 1000 student. This was a drop of 34 per 1000 students from 2009 and a significant decline from the rate of students who placed themselves in those categories when self-ratings of emotional health were first measured in 1985.
-Consider the rate in 1985 as the baseline rate. This rate was 636 per 1000 students. What was the decrease in the rate of students who reported that their emotional health was in the "highest 10 percent" or "above average" as compared to this baseline rate?

Accepted Answer

The answer of Use the following information for questions:
 First-year...

Question 13

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 The next three questions are based on a study (part of the Women's Health Initiative) of healthy women volunteers. A total of 16,608 women were randomly assigned to take either placebo or a popular hormone replacement therapy (HRT) for eight years. The study was stopped after 5 years in part because the women on HRT had a higher rate of heart attacks than the placebo group.
-The rate of invasive breast cancer was 30 per 10,000 women in the placebo group and 38 per 10,000 women in the HRT group. What was the increase in the rate of breast cancers in the HRT group compared to the rate in the placebo group?

Accepted Answer

The answer of Use the following information for questions:
 The...

Question 14

If a difference seen in sample results is "statistically significant"it means that

Accepted Answer

A)  there is an important difference in the sample results. 
B)  there is an important difference in the population. 
C)  the difference observed in the sample was unlikely to have occurred if there is no difference in the population. 
D)  there is an important difference in the population that wasn't reflected in the sample results.

Question 15

A randomized experiment was done by randomly assigning each participant either to walk for half an hour three times a week or to sit quietly reading a book for half an hour three times a week. At the end of a year the change in participants' blood pressure over the year was measured, and the change was compared for the two groups.
-This is a randomized experiment rather than an observational study because

Accepted Answer

A)  blood pressure was measured at the beginning and end of the study. 
B)  the two groups were compared at the end of the study. 
C)  the participants were randomly assigned to either walk or read, rather than choosing their own activity. 
D)  a random sample of participants was used.

Question 16

Drawn below are two dotplots displaying the number of minutes spent exercising during a typical week for 36 female and 39 male students at Penn State University. Also given are the five number summaries. Describe any differences or similarities between the two sets of data.

Accepted Answer

The answer of Drawn below are two dotplots displaying the...

Question 17

Which of the following is true about a dotplot and a five-number summary?

Accepted Answer

A)  A dotplot displays all of the individual responses while a five-number summary does not. 
B)  A five-number summary displays all of the individual responses while a dotplot does not. 
C)  Both a dotplot and a five-number summary display all of the individual responses. 
D)  Neither a dotplot nor a five-number summary displays all of the individual responses.

Question 18

Use the following information for questions:
 According to a CNN poll released in January of 2010, 56 percent of the public opposed the stimulus bill, with 42 percent supportive of the plan. The CNN/Opinion Research Corporation poll was conducted January 8-10, with 1,021 adult Americans questioned by telephone. The survey's sampling error was reported as plus or minus 3 percentage points.
-In March of 2009, just weeks after the stimulus was signed into law by President Obama, a CNN survey indicated that 54 percent supported the program, with 44 percent opposed. If we wish to compare the supporting rates between 2010 and 2009, what would be the base rate?

Accepted Answer

The answer of Use the following information for questions:
 According...

Question 19

A newspaper reported that 41% of students who had taken calculus in high school had a first year college GPA (grade point average) of 3.2 or higher. Explain why it would also have been useful to know what the baseline rate was (i.e. the proportion of students without calculus who had a GPA of 3.2 or higher).

Accepted Answer

The answer of A newspaper reported that 41% of students...

Exam 1: Statistics Success Stories and Cautionary Tales