Deck 27: Putting What You Have Learned to the Test

Question 1

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} Name one of the confounding factors not controlled for in this study.

Answer 1

any reasonable answer ok. Examples: number of school days missed; age of the parents; quality of the schools attended; teachers' attitudes; level of support; etc.

Question 2

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} This was most likely what type of observational study?

A)A prospective study.
B)A retrospective study.
C)A matched-pairs study.
D)None of the above.

Answer 2

A retrospective study.

Question 3

CASE STUDY 27.1
ACTING OUT YOUR DREAMS
For Questions , use the following narrative
Narrative: Case study 27.1 summary
A sample of undergraduate psychology students were randomly divided into three groups and asked about their experiences with acting out dreams while dreaming.Group 1 was asked "On how many nights did the following occur in the last year … acting out a dream (while dreaming)?" Group 2 was asked the same question as Group 1, but with some examples given of "acting out a dream while dreaming", such as crying, laughing, making arm/ leg movements.Group 3 was given a specific list of dream-state actions and asked which of these they had experienced.That is, the subjects in Group 3 did not need to synthesize their own interpretation of the phrase "acting out a dream" or conceive of their own example actions.The proportions of positive responses for Groups 1, 2, and 3 were 35.9%, 76.7%, and 98.2%, respectively.

For Group 1, how might "acting out a dream (while dreaming)" be misinterpreted?

Answer 3

With no other guidance as to its meaning, some subjects might have interpreted "acting out a dream" as "dreaming that your were dreaming".others might have thought the question refered to dreaming about "living one's dreams".

Question 4

CASE STUDY 27.1
ACTING OUT YOUR DREAMS
For Questions , use the following narrative
Narrative: Case study 27.1 summary
A sample of undergraduate psychology students were randomly divided into three groups and asked about their experiences with acting out dreams while dreaming.Group 1 was asked "On how many nights did the following occur in the last year … acting out a dream (while dreaming)?" Group 2 was asked the same question as Group 1, but with some examples given of "acting out a dream while dreaming", such as crying, laughing, making arm/ leg movements.Group 3 was given a specific list of dream-state actions and asked which of these they had experienced.That is, the subjects in Group 3 did not need to synthesize their own interpretation of the phrase "acting out a dream" or conceive of their own example actions.The proportions of positive responses for Groups 1, 2, and 3 were 35.9%, 76.7%, and 98.2%, respectively.

{Case study 27.1 narrative} What type of study was this?

A)A matched-pairs study.
B)A prospective study.
C)An observational study.
D)A randomized experiment.

Question 5

CASE STUDY 27.5
YOU CAN WORK AND GET YOUR EXERCISE AT THE SAME TIME
For Questions , use the following narrative
Narrative: Case study 27.5 summary
One in five clerical workers walks about a quarter mile a day just to complete routine functions like faxing, copying, and filing, a national survey on office efficiency reports.The survey also shows that the average office worker spends close to 15 percent of the day just walking around the office.

{Case study 27.5 narrative} What type of study was this?

A)An observational study.
B)A randomized experiment.
C)A meta-analysis.
D)Not enough information to tell.

Question 6

CASE STUDY 27.4
IT REALLY IS TRUE ABOUT ASPIRIN
For Questions , use the following narrative
Narrative: Case study 27.4 summary
This study was a meta-analysis of clinical trials in which aspirin was used to prevent blood clots.The meta-analysis (covering both aspirin and more expensive anti-platelet drugs) combined the results of 300 trials involving 140,000 patients.Its recommendation: a regime of half a tablet of aspirin a day is valuable for all victims of heart attack and stroke, and other at-risk patients such as angina sufferers and recipients of coronary bypass grafts.The lead researcher was quoted as saying "This is one of the most cost-effective drug interventions one could have in developed countries."

{Case study 27.4 narrative} Some of the methodologically suspicious studies lacked double-blinding.What effect can this have on the results of a study?

A)The results will likely be biased.
B)The results won't be shown to the public.
C)The margin of error for the statistics calculated will be increased.
D)All of the above.

Question 7

CASE STUDY 27.4
IT REALLY IS TRUE ABOUT ASPIRIN
For Questions , use the following narrative
Narrative: Case study 27.4 summary
This study was a meta-analysis of clinical trials in which aspirin was used to prevent blood clots.The meta-analysis (covering both aspirin and more expensive anti-platelet drugs) combined the results of 300 trials involving 140,000 patients.Its recommendation: a regime of half a tablet of aspirin a day is valuable for all victims of heart attack and stroke, and other at-risk patients such as angina sufferers and recipients of coronary bypass grafts.The lead researcher was quoted as saying "This is one of the most cost-effective drug interventions one could have in developed countries."

{Case study 27.4 narrative} What type of study was this?

A)An observational study.
B)A randomized experiment.
C)A type that uses a collection of statistical techniques for combining studies.
D)None of the above.

Question 8

CASE STUDY 27.2
CRANBERRY JUICE AND BLADDER INFECTIONS
For Questions , use the following narrative
Narrative: Case study 27.2 summary
Researchers compared urinary bacteria levels of elderly women who drank 10 ounces of a juice drink containing cranberry juice each day to elderly women who consumed the same amount of a look-alike drink without cranberry juice (indistinguishable in taste, appearance, and vitamin C content from cranberry juice).153 elderly women participated in this study.Each one was randomly assigned to the cranberry juice group or the placebo group and was followed over a 6-month period.The women had a mean age of 78.5 years and high levels of bacteria in their urine at the start of the study.The odds in the cranberry group of having bacteria levels exceeding a certain threshold were 42% of what they were in the control group.

{Case study 27.2 narrative} What can you conclude, based on this research, about cranberry juice and urinary tract bacteria?

Question 9

CASE STUDY 27.2
CRANBERRY JUICE AND BLADDER INFECTIONS
For Questions , use the following narrative
Narrative: Case study 27.2 summary
Researchers compared urinary bacteria levels of elderly women who drank 10 ounces of a juice drink containing cranberry juice each day to elderly women who consumed the same amount of a look-alike drink without cranberry juice (indistinguishable in taste, appearance, and vitamin C content from cranberry juice).153 elderly women participated in this study.Each one was randomly assigned to the cranberry juice group or the placebo group and was followed over a 6-month period.The women had a mean age of 78.5 years and high levels of bacteria in their urine at the start of the study.The odds in the cranberry group of having bacteria levels exceeding a certain threshold were 42% of what they were in the control group.

{Case study 27.2 narrative} Which negative effect was not being controlled for by using the placebo drink?

A)The placebo effect.
B)The interaction effect.
C)The experimenter effect.
D)All of the above were being controlled for with the placebo drink.

Question 10

CASE STUDY 27.5
YOU CAN WORK AND GET YOUR EXERCISE AT THE SAME TIME
For Questions , use the following narrative
Narrative: Case study 27.5 summary
One in five clerical workers walks about a quarter mile a day just to complete routine functions like faxing, copying, and filing, a national survey on office efficiency reports.The survey also shows that the average office worker spends close to 15 percent of the day just walking around the office.

{Case study 27.5 narrative} The statistics presented in the summary above are very difficult to interpret.What is one of the issues you have with interpreting the statistics given?

Question 11

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} The researchers seem to be saying (or at least implying) that moving is the cause of these problems.Is that an appropriate conclusion? Explain.

Question 12

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} The sample size in this study is very large, which may cause some problems.Explain why, and what was missing from the results that might have helped the reader determine the magnitude of the differences observed.

Question 13

CASE STUDY 27.2
CRANBERRY JUICE AND BLADDER INFECTIONS
For Questions , use the following narrative
Narrative: Case study 27.2 summary
Researchers compared urinary bacteria levels of elderly women who drank 10 ounces of a juice drink containing cranberry juice each day to elderly women who consumed the same amount of a look-alike drink without cranberry juice (indistinguishable in taste, appearance, and vitamin C content from cranberry juice).153 elderly women participated in this study.Each one was randomly assigned to the cranberry juice group or the placebo group and was followed over a 6-month period.The women had a mean age of 78.5 years and high levels of bacteria in their urine at the start of the study.The odds in the cranberry group of having bacteria levels exceeding a certain threshold were 42% of what they were in the control group.

{Case study 27.2 narrative} What type of study was this?

A)An observational study.
B)A prospective study.
C)A retrospective study.
D)A randomized experiment.

Question 14

CASE STUDY 27.5
YOU CAN WORK AND GET YOUR EXERCISE AT THE SAME TIME
For Questions , use the following narrative
Narrative: Case study 27.5 summary
One in five clerical workers walks about a quarter mile a day just to complete routine functions like faxing, copying, and filing, a national survey on office efficiency reports.The survey also shows that the average office worker spends close to 15 percent of the day just walking around the office.

{Case study 27.5 narrative} The survey was commissioned by Canon U.S.A., maker of office copiers and printers that claim to cut the time and money "spent running from one machine to the next." In what way might this cause a problem for the results of the study?

Question 15

CASE STUDY 27.4
IT REALLY IS TRUE ABOUT ASPIRIN
For Questions , use the following narrative
Narrative: Case study 27.4 summary
This study was a meta-analysis of clinical trials in which aspirin was used to prevent blood clots.The meta-analysis (covering both aspirin and more expensive anti-platelet drugs) combined the results of 300 trials involving 140,000 patients.Its recommendation: a regime of half a tablet of aspirin a day is valuable for all victims of heart attack and stroke, and other at-risk patients such as angina sufferers and recipients of coronary bypass grafts.The lead researcher was quoted as saying "This is one of the most cost-effective drug interventions one could have in developed countries."

{Case study 27.4 narrative} The researchers analyzing a smaller subset of the studies in a meta-analysis were not able to find statistical significance.Give two reasons why this might be.

Question 16

CASE STUDY 27.1
ACTING OUT YOUR DREAMS
For Questions , use the following narrative
Narrative: Case study 27.1 summary
A sample of undergraduate psychology students were randomly divided into three groups and asked about their experiences with acting out dreams while dreaming.Group 1 was asked "On how many nights did the following occur in the last year … acting out a dream (while dreaming)?" Group 2 was asked the same question as Group 1, but with some examples given of "acting out a dream while dreaming", such as crying, laughing, making arm/ leg movements.Group 3 was given a specific list of dream-state actions and asked which of these they had experienced.That is, the subjects in Group 3 did not need to synthesize their own interpretation of the phrase "acting out a dream" or conceive of their own example actions.The proportions of positive responses for Groups 1, 2, and 3 were 35.9%, 76.7%, and 98.2%, respectively.

{Case study 27.1 narrative} What do you think is the most interesting aspect of this study?

Question 17

CASE STUDY 27.5
YOU CAN WORK AND GET YOUR EXERCISE AT THE SAME TIME
For Questions , use the following narrative
Narrative: Case study 27.5 summary
One in five clerical workers walks about a quarter mile a day just to complete routine functions like faxing, copying, and filing, a national survey on office efficiency reports.The survey also shows that the average office worker spends close to 15 percent of the day just walking around the office.

{Case study 27.5 narrative} Why is it not possible to even evaluate the results of this study?

A)The results might be biased because they were sponsored by Canon U.S.A.
B)There is no information on how many people were involved in the study.
C)We don't know how the data were collected.
D)All of the above.

Question 18

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} Discuss how the age of the child can affect the results of this study.

Question 19

CASE STUDY 27.4
IT REALLY IS TRUE ABOUT ASPIRIN
For Questions , use the following narrative
Narrative: Case study 27.4 summary
This study was a meta-analysis of clinical trials in which aspirin was used to prevent blood clots.The meta-analysis (covering both aspirin and more expensive anti-platelet drugs) combined the results of 300 trials involving 140,000 patients.Its recommendation: a regime of half a tablet of aspirin a day is valuable for all victims of heart attack and stroke, and other at-risk patients such as angina sufferers and recipients of coronary bypass grafts.The lead researcher was quoted as saying "This is one of the most cost-effective drug interventions one could have in developed countries."

{Case study 27.4 narrative} When the pool of studies examined was reduced to include only those following any type of surgery, the results were still found to be statistically significant.Yet when the pool of studies was reduced a third time, to include only those studies that followed 'general' surgery (vs.other types of surgery, such as orthopedic surgery), the results were not found to be statistically significant.Does this mean there is no real effect of aspirin for patients following general surgery? Explain.

Question 20

CASE STUDY 27.3
CHILDREN ON THE GO
For Questions , use the following narrative
Narrative: Case study 27.3 summary
The researchers of this study concluded that children who move often are 35 percent more likely to fail a grade and 77 percent more likely to have behavioral problems than children whose families move rarely.These results were based on a nationwide study of 9,915 youngsters aged 6-17."High movers" were defined as those who had moved at least 6 times.High movers were 1.35 times more likely to have failed a grade and 1.77 times more likely to have developed at least four frequent behavioral problems (ranging from depression to impulsiveness to destructiveness).The results were adjusted for poverty, single parenting, belonging to a racial minority, and having parents with less than a high school education.

{Case study 27.3 narrative} The data were based on surveys completed by the parents.How can this affect the results of the study?

A)Some parents may not be as willing as others to admit that their children are having problems, resulting in biased data.
B)There could be a higher rate of nonresponse for the "high movers" group compared to the others, which could cause bias.
C)Parents may not be as adept as medical professionals at judging behavioral problems, or as adept as school teachers at judging grade issues, so the results may not be accurate.
D)All of the above.

Question 21

CASE STUDY 27.7
UNPALATABLE PATE
For Questions , use the following narrative
Narrative: Case study 27.7 summary
News article excerpt: An exploratory study asked roughly 300 Australian students whether they approved or disapproved of certain uses of animals.Researchers concluded that students frequently condemned consumptive practices while endorsing consumption itself.For example, nearly three-fourths of the students disapproved of "force-feeding geese to make their livers swell up to produce pate for restaurants" but the majority did not disapprove of "eating pate produced by the force-feeding of geese." The authors interpreted these findings as evidence of an inconsistency between people's attitudes and behaviors toward the use of animals.

{Case study 27.7 narrative} What type of study was this?

A)An observational study.
B)A randomized experiment.
C)A meta-analysis.
D)Not enough information to tell.

Question 22

CASE STUDY 27.6
SEX, ALCOHOL, AND THE FIRST DATE
For Questions , use the following narrative
Narrative: Case study 27.6 summary
Young couples are much more likely to have sex on their first date if the male partner drinks alcohol and the woman doesn't, new research shows.The study was based on interviews with 2,052 teenagers.They reported having sex on a first date only 6% of the time if the female drank alcohol while the male did not, compared to 8% of the time when neither partner drank.Nineteen percent of the teens reported having sex when both partners drank, but the highest frequency of sex on the first date - 24 percent - was reported when only the male drank.

{Case study 27.6 narrative} The margin of error for these results is about plus or minus 2%.What real meaning does the margin of error have for this particular study, in terms of making conclusions about the population percentages?

A)It means that you have to add and subtract 2% from each of the percentages stated in the study, to get an idea of what the population percentages are for all teenagers.
B)It means that the bias in the results is measured to be about 2% in either direction.
C)The margin of error in this case has very little meaning because of the severe bias in the data in terms of how it was collected.The percentages quoted in the article are most likely off to begin with.
D)The sample results will differ from the true value in the population by at most 2% in either direction, due to sampling error.

Question 23

CASE STUDY 27.9
SO YOU THOUGHT SPINACH WAS GOOD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.9 summary
A study published in the New England Journal of Medicine shows that the antioxidant beta-carotene markedly increased the incidence of lung cancer among heavy smokers in Finland.Incidence of lung cancer was 18% higher among the 14,500 smokers who took beta-carotene than among the 14,500 who didn't.The probability that the observed increase was due to chance is less than one in one hundred.(A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty.)This result was particularly worrying to researchers and the media, because it comes from a large, randomized clinical trial, yet it goes against all the previously available evidence.Over a hundred epidemiologic studies indicate that people who have high levels of beta-carotene in their diet and in their blood have lower risks of cancer, particularly lung cancer.

{Case study 27.9 narrative} What type of study was this?

A)An observational study.
B)An experiment.
C)A meta-analysis.
D)Not enough information to tell.

Question 24

CASE STUDY 27.7
UNPALATABLE PATE
For Questions , use the following narrative
Narrative: Case study 27.7 summary
News article excerpt: An exploratory study asked roughly 300 Australian students whether they approved or disapproved of certain uses of animals.Researchers concluded that students frequently condemned consumptive practices while endorsing consumption itself.For example, nearly three-fourths of the students disapproved of "force-feeding geese to make their livers swell up to produce pate for restaurants" but the majority did not disapprove of "eating pate produced by the force-feeding of geese." The authors interpreted these findings as evidence of an inconsistency between people's attitudes and behaviors toward the use of animals.

{Case study 27.7 narrative} This is an excellent example of a survey where wording of the questions can greatly affect the results.Comment on the wording of the question, "Do you approve or disapprove of force-feeding geese to make their livers swell up to produce pate for restaurants?" and suggest how the question should be rewritten if you find problems with it.

Question 25

CASE STUDY 27.6
SEX, ALCOHOL, AND THE FIRST DATE
For Questions , use the following narrative
Narrative: Case study 27.6 summary
Young couples are much more likely to have sex on their first date if the male partner drinks alcohol and the woman doesn't, new research shows.The study was based on interviews with 2,052 teenagers.They reported having sex on a first date only 6% of the time if the female drank alcohol while the male did not, compared to 8% of the time when neither partner drank.Nineteen percent of the teens reported having sex when both partners drank, but the highest frequency of sex on the first date - 24 percent - was reported when only the male drank.

{Case study 27.6 narrative} There may be a real problem with bias in how the data was collected, leading to incorrect statistics.Explain.

Question 26

CASE STUDY 27.9
SO YOU THOUGHT SPINACH WAS GOOD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.9 summary
A study published in the New England Journal of Medicine shows that the antioxidant beta-carotene markedly increased the incidence of lung cancer among heavy smokers in Finland.Incidence of lung cancer was 18% higher among the 14,500 smokers who took beta-carotene than among the 14,500 who didn't.The probability that the observed increase was due to chance is less than one in one hundred.(A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty.)This result was particularly worrying to researchers and the media, because it comes from a large, randomized clinical trial, yet it goes against all the previously available evidence.Over a hundred epidemiologic studies indicate that people who have high levels of beta-carotene in their diet and in their blood have lower risks of cancer, particularly lung cancer.

{Case study 27.9 narrative} "The probability that the observed increase in lung cancer was due to chance is less than one in one hundred." What is this equivalent to saying?

A)The p-value is less than .01.
B)The results of the study are not statistically significant.
C)The significance level associated with this test is less than .01.
D)None of the above.

Question 27

CASE STUDY 27.8
NURSING MOMS CAN EXERCISE, TOO
For Questions , use the following narrative
Narrative: Case study 27.8 summary
Moderate aerobic exercise has no adverse effects on the quantity or quality of breast milk produced by nursing mothers, and can significantly improve the mothers' cardiovascular fitness, researchers say.The study monitored 33 women for 12 weeks, beginning 6-8 weeks after the births of their children.All were exclusively breast-feeding their babies, and had not previously been exercising.18 women were randomly assigned to the exercise group and 15 to the non-exercise group.The women in the exercise group participated in individual exercise programs, including rapid walking, jogging or bicycling for 45 minutes per day, five days per week.The researchers found that: 1) women in both groups experienced the same amount of weight loss; 2) there was an important improvement in the aerobic fitness of the exercising mothers; and 3) there was no significant difference between the groups in terms of infant breast-milk intake, energy output in the milk, or infant weight gain.

{Case study 27.8 narrative} The p-value for testing the difference in infant weight gain for the exercise group versus the control group over the time of the study was found to be .86.Explain, in terms that a non-statistics student would understand, what this p-value means.

Question 28

CASE STUDY 27.8
NURSING MOMS CAN EXERCISE, TOO
For Questions , use the following narrative
Narrative: Case study 27.8 summary
Moderate aerobic exercise has no adverse effects on the quantity or quality of breast milk produced by nursing mothers, and can significantly improve the mothers' cardiovascular fitness, researchers say.The study monitored 33 women for 12 weeks, beginning 6-8 weeks after the births of their children.All were exclusively breast-feeding their babies, and had not previously been exercising.18 women were randomly assigned to the exercise group and 15 to the non-exercise group.The women in the exercise group participated in individual exercise programs, including rapid walking, jogging or bicycling for 45 minutes per day, five days per week.The researchers found that: 1) women in both groups experienced the same amount of weight loss; 2) there was an important improvement in the aerobic fitness of the exercising mothers; and 3) there was no significant difference between the groups in terms of infant breast-milk intake, energy output in the milk, or infant weight gain.

{Case study 27.8 narrative} Name one confounding variable that was controlled for in this study.

Question 29

CASE STUDY 27.9
SO YOU THOUGHT SPINACH WAS GOOD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.9 summary
A study published in the New England Journal of Medicine shows that the antioxidant beta-carotene markedly increased the incidence of lung cancer among heavy smokers in Finland.Incidence of lung cancer was 18% higher among the 14,500 smokers who took beta-carotene than among the 14,500 who didn't.The probability that the observed increase was due to chance is less than one in one hundred.(A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty.)This result was particularly worrying to researchers and the media, because it comes from a large, randomized clinical trial, yet it goes against all the previously available evidence.Over a hundred epidemiologic studies indicate that people who have high levels of beta-carotene in their diet and in their blood have lower risks of cancer, particularly lung cancer.

{Case study 27.9 narrative} Explain why we should perhaps not be surprised by the results of this study, in light of all the studies that had been done before.(Assume that the quality of the studies is not an issue.)

Question 30

CASE STUDY 27.6
SEX, ALCOHOL, AND THE FIRST DATE
For Questions , use the following narrative
Narrative: Case study 27.6 summary
Young couples are much more likely to have sex on their first date if the male partner drinks alcohol and the woman doesn't, new research shows.The study was based on interviews with 2,052 teenagers.They reported having sex on a first date only 6% of the time if the female drank alcohol while the male did not, compared to 8% of the time when neither partner drank.Nineteen percent of the teens reported having sex when both partners drank, but the highest frequency of sex on the first date - 24 percent - was reported when only the male drank.

{Case study 27.6 narrative}What type of study was this?

A)An observational study.
B)A randomized experiment.
C)A matched-pairs experiment.
D)Not enough information to tell.

Question 31

CASE STUDY 27.9
SO YOU THOUGHT SPINACH WAS GOOD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.9 summary
A study published in the New England Journal of Medicine shows that the antioxidant beta-carotene markedly increased the incidence of lung cancer among heavy smokers in Finland.Incidence of lung cancer was 18% higher among the 14,500 smokers who took beta-carotene than among the 14,500 who didn't.The probability that the observed increase was due to chance is less than one in one hundred.(A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty.)This result was particularly worrying to researchers and the media, because it comes from a large, randomized clinical trial, yet it goes against all the previously available evidence.Over a hundred epidemiologic studies indicate that people who have high levels of beta-carotene in their diet and in their blood have lower risks of cancer, particularly lung cancer.

{Case study 27.9 narrative} "A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty." What is this equivalent to saying?

A)The p-value is 1/20 = .05.
B)The results of the study are not statistically significant.
C)The significance level associated with this test is .05.
D)None of the above.

Question 32

CASE STUDY 27.7
UNPALATABLE PATE
For Questions , use the following narrative
Narrative: Case study 27.7 summary
News article excerpt: An exploratory study asked roughly 300 Australian students whether they approved or disapproved of certain uses of animals.Researchers concluded that students frequently condemned consumptive practices while endorsing consumption itself.For example, nearly three-fourths of the students disapproved of "force-feeding geese to make their livers swell up to produce pate for restaurants" but the majority did not disapprove of "eating pate produced by the force-feeding of geese." The authors interpreted these findings as evidence of an inconsistency between people's attitudes and behaviors toward the use of animals.

{Case study 27.7 narrative} The authors have over interpreted their results in the last sentence of the above summary.Explain.

Question 33

CASE STUDY 27.8
NURSING MOMS CAN EXERCISE, TOO
For Questions , use the following narrative
Narrative: Case study 27.8 summary
Moderate aerobic exercise has no adverse effects on the quantity or quality of breast milk produced by nursing mothers, and can significantly improve the mothers' cardiovascular fitness, researchers say.The study monitored 33 women for 12 weeks, beginning 6-8 weeks after the births of their children.All were exclusively breast-feeding their babies, and had not previously been exercising.18 women were randomly assigned to the exercise group and 15 to the non-exercise group.The women in the exercise group participated in individual exercise programs, including rapid walking, jogging or bicycling for 45 minutes per day, five days per week.The researchers found that: 1) women in both groups experienced the same amount of weight loss; 2) there was an important improvement in the aerobic fitness of the exercising mothers; and 3) there was no significant difference between the groups in terms of infant breast-milk intake, energy output in the milk, or infant weight gain.

{Case study 27.8 narrative} Suppose the results had been stated this way: "The p-value for the test of equal means for maximal oxygen uptake (a measurement of cardiovascular fitness) for the exercise group versus the non-exercise group was found to be less than .001." What could you conclude, just from this sentence alone, and no other results?

A)The difference in the means was found to be statistically significant.
B)The mean for the exercise group was significantly higher than for the non-exercise group.
C)The mean for the exercise group was significantly lower than for the non-exercise group.
D)The difference in the means was not found to be statistically significant.

Question 34

CASE STUDY 27.8
NURSING MOMS CAN EXERCISE, TOO
For Questions , use the following narrative
Narrative: Case study 27.8 summary
Moderate aerobic exercise has no adverse effects on the quantity or quality of breast milk produced by nursing mothers, and can significantly improve the mothers' cardiovascular fitness, researchers say.The study monitored 33 women for 12 weeks, beginning 6-8 weeks after the births of their children.All were exclusively breast-feeding their babies, and had not previously been exercising.18 women were randomly assigned to the exercise group and 15 to the non-exercise group.The women in the exercise group participated in individual exercise programs, including rapid walking, jogging or bicycling for 45 minutes per day, five days per week.The researchers found that: 1) women in both groups experienced the same amount of weight loss; 2) there was an important improvement in the aerobic fitness of the exercising mothers; and 3) there was no significant difference between the groups in terms of infant breast-milk intake, energy output in the milk, or infant weight gain.

{Case study 27.8 narrative} Having individual exercise programs for the women in the exercise group does what for this experiment?

A)Increases ecological validity.
B)Creates bias.
C)Makes the results less generalizeable to the population.
D)None of the above.

Question 35

CASE STUDY 27.8
NURSING MOMS CAN EXERCISE, TOO
For Questions , use the following narrative
Narrative: Case study 27.8 summary
Moderate aerobic exercise has no adverse effects on the quantity or quality of breast milk produced by nursing mothers, and can significantly improve the mothers' cardiovascular fitness, researchers say.The study monitored 33 women for 12 weeks, beginning 6-8 weeks after the births of their children.All were exclusively breast-feeding their babies, and had not previously been exercising.18 women were randomly assigned to the exercise group and 15 to the non-exercise group.The women in the exercise group participated in individual exercise programs, including rapid walking, jogging or bicycling for 45 minutes per day, five days per week.The researchers found that: 1) women in both groups experienced the same amount of weight loss; 2) there was an important improvement in the aerobic fitness of the exercising mothers; and 3) there was no significant difference between the groups in terms of infant breast-milk intake, energy output in the milk, or infant weight gain.

{Case study 27.8 narrative} Suppose the results had been based on 330 women (180 in the exercise group and 150 in the non-exercise group) rather than 33 women.How would the p-values have changed, given that the reported sample means remained the same?

A)The p-values for the sample of 330 would have been larger than the p-values for the sample of 33.
B)The p-values for the sample of 330 would have been smaller than the p-values for the sample of 33.
C)The p-values for the significant results would have been smaller for the sample of 330 (compared to the sample of 33), while the p-values for the non-significant results would have been larger for the sample of 330 (compared to the sample of 33).
D)The p-values would not have changed.

Question 36

CASE STUDY 27.9
SO YOU THOUGHT SPINACH WAS GOOD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.9 summary
A study published in the New England Journal of Medicine shows that the antioxidant beta-carotene markedly increased the incidence of lung cancer among heavy smokers in Finland.Incidence of lung cancer was 18% higher among the 14,500 smokers who took beta-carotene than among the 14,500 who didn't.The probability that the observed increase was due to chance is less than one in one hundred.(A difference in such studies is taken seriously when the probability that it happened by chance is less than one in twenty.)This result was particularly worrying to researchers and the media, because it comes from a large, randomized clinical trial, yet it goes against all the previously available evidence.Over a hundred epidemiologic studies indicate that people who have high levels of beta-carotene in their diet and in their blood have lower risks of cancer, particularly lung cancer.

{Case study 27.9 narrative} What does the following statement mean, in statistical notation and terms? "The probability that the observed increase in lung cancer was due to chance is less than one in one hundred."

Question 37

CASE STUDY 27.10
CHILL OUT-MOVE TO HONOLULU
For Questions , use the following narrative
Narrative: Case study 27.10 summary
This study was based on a poll that measured citizens' hostility levels and compared them with their cities' death rates.The research findings were reporting as the following: 1) people with higher hostility levels have higher rates of heart disease deaths and overall deaths; 2) cities with higher hostility scores consistently had higher death rates; 3) cities with lower hostility scores had lower death rates.The results were summarized by saying "Hostile cities may want to chill out." The study was based on 10 cities, one from each of the states with the five highest and five lowest heart disease death rates.Philadelphia had the highest levels of both (hostility and death rate), and Honolulu had the lowest levels of both (hostility and death rate).It was reported that statistically, the probability of the observed correlation between hostility and death rate occurring by chance is less than 1 in 10,000.

{Case study 27.10 narrative} The main implication by the researchers (and the media) about the results of this study is that if cities like Philadelphia would lower their hostility index, they would also lower their death rates.Is that a valid conclusion? Explain why or why not.

Question 38

CASE STUDY 27.7
UNPALATABLE PATE
For Questions , use the following narrative
Narrative: Case study 27.7 summary
News article excerpt: An exploratory study asked roughly 300 Australian students whether they approved or disapproved of certain uses of animals.Researchers concluded that students frequently condemned consumptive practices while endorsing consumption itself.For example, nearly three-fourths of the students disapproved of "force-feeding geese to make their livers swell up to produce pate for restaurants" but the majority did not disapprove of "eating pate produced by the force-feeding of geese." The authors interpreted these findings as evidence of an inconsistency between people's attitudes and behaviors toward the use of animals.

{Case study 27.7 narrative} It appears that the researchers only offered two choices for answers to their questions: approve or disapprove.What is the impact of this on the results of the survey?

A)It overstates the results in a biased way; some people may have a neutral opinion but that was not a choice."Not disapproving" is different from "approving."
B)It forces people to really think about their feelings and commit one way or the other.This will give better results.
C)It will not impact the results at all.
D)None of the above.

Question 39

CASE STUDY 27.10
CHILL OUT-MOVE TO HONOLULU
For Questions , use the following narrative
Narrative: Case study 27.10 summary
This study was based on a poll that measured citizens' hostility levels and compared them with their cities' death rates.The research findings were reporting as the following: 1) people with higher hostility levels have higher rates of heart disease deaths and overall deaths; 2) cities with higher hostility scores consistently had higher death rates; 3) cities with lower hostility scores had lower death rates.The results were summarized by saying "Hostile cities may want to chill out." The study was based on 10 cities, one from each of the states with the five highest and five lowest heart disease death rates.Philadelphia had the highest levels of both (hostility and death rate), and Honolulu had the lowest levels of both (hostility and death rate).It was reported that statistically, the probability of the observed correlation between hostility and death rate occurring by chance is less than 1 in 10,000.

{Case study 27.10 narrative} Name one of the confounding variables in this study.

Question 40

CASE STUDY 27.6
SEX, ALCOHOL, AND THE FIRST DATE
For Questions , use the following narrative
Narrative: Case study 27.6 summary
Young couples are much more likely to have sex on their first date if the male partner drinks alcohol and the woman doesn't, new research shows.The study was based on interviews with 2,052 teenagers.They reported having sex on a first date only 6% of the time if the female drank alcohol while the male did not, compared to 8% of the time when neither partner drank.Nineteen percent of the teens reported having sex when both partners drank, but the highest frequency of sex on the first date - 24 percent - was reported when only the male drank.

{Case study 27.6 narrative} This is an excellent example of an observational study where the results were misinterpreted.Explain.

Question 41

CASE STUDY 27.11
SO YOU THOUGHT HOT DOGS WERE BAD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.11 summary
In a magazine article, three research groups reported a link between cured-meat consumption and cancer.Among 232 cases in one study, children who ate 12 or more hot dots in a month were nine times as likely as hot dog-free controls to develop leukemia.Researchers also found an increased risk for kids whose fathers ate a lot of hot dogs.Another study involving 234 cases of various childhood cancers found that children whose mothers ate hot dogs at least once a week were twice as likely as controls to develop brain tumors.The results may be due to the N-nitroso compounds in cured meats, researchers say.However, they warn that the studies are far from conclusive.

{Case study 27.11 narrative} What is one of the problems with trying to link diet to cancer in a study such as this one?

A)People have poor memories about what they ate years ago.
B)People aren't necessarily going to report their diets truthfully.
C)Parents searching for an answer to why their child has cancer are probably more likely to "remember" feeding the child an unhealthful diet than parents whose children do not have cancer.
D)All of the above.

Question 42

CASE STUDY 27.10
CHILL OUT-MOVE TO HONOLULU
For Questions , use the following narrative
Narrative: Case study 27.10 summary
This study was based on a poll that measured citizens' hostility levels and compared them with their cities' death rates.The research findings were reporting as the following: 1) people with higher hostility levels have higher rates of heart disease deaths and overall deaths; 2) cities with higher hostility scores consistently had higher death rates; 3) cities with lower hostility scores had lower death rates.The results were summarized by saying "Hostile cities may want to chill out." The study was based on 10 cities, one from each of the states with the five highest and five lowest heart disease death rates.Philadelphia had the highest levels of both (hostility and death rate), and Honolulu had the lowest levels of both (hostility and death rate).It was reported that statistically, the probability of the observed correlation between hostility and death rate occurring by chance is less than 1 in 10,000.

{Case study 27.10 narrative} It was reported that statistically, the probability that the observed correlation between hostility and death rate occurred by chance is less than 1 in 10,000.What is your reaction to this statement?

A)This sounds about right, given that 10 entire cities were studied.
B)This can't be right; only the top and bottom five states were used; these are outliers by definition, and can strongly affect the correlation and hypothesis tests about it.
C)There is not enough information to effectively evaluate this statement.
D)It has to be correct; it was reported in a news article.

Question 43

CASE STUDY 27.11
SO YOU THOUGHT HOT DOGS WERE BAD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.11 summary
In a magazine article, three research groups reported a link between cured-meat consumption and cancer.Among 232 cases in one study, children who ate 12 or more hot dots in a month were nine times as likely as hot dog-free controls to develop leukemia.Researchers also found an increased risk for kids whose fathers ate a lot of hot dogs.Another study involving 234 cases of various childhood cancers found that children whose mothers ate hot dogs at least once a week were twice as likely as controls to develop brain tumors.The results may be due to the N-nitroso compounds in cured meats, researchers say.However, they warn that the studies are far from conclusive.

{Case study 27.11 narrative} What important statistical information is missing that would have helped to put the 'nine times as likely to develop leukemia' result into proper perspective?

Question 44

CASE STUDY 27.10
CHILL OUT-MOVE TO HONOLULU
For Questions , use the following narrative
Narrative: Case study 27.10 summary
This study was based on a poll that measured citizens' hostility levels and compared them with their cities' death rates.The research findings were reporting as the following: 1) people with higher hostility levels have higher rates of heart disease deaths and overall deaths; 2) cities with higher hostility scores consistently had higher death rates; 3) cities with lower hostility scores had lower death rates.The results were summarized by saying "Hostile cities may want to chill out." The study was based on 10 cities, one from each of the states with the five highest and five lowest heart disease death rates.Philadelphia had the highest levels of both (hostility and death rate), and Honolulu had the lowest levels of both (hostility and death rate).It was reported that statistically, the probability of the observed correlation between hostility and death rate occurring by chance is less than 1 in 10,000.

{Case study 27.10 narrative} What type of study was this?

A)An observational study.
B)A randomized experiment.
C)A meta-analysis.
D)Not enough information to tell.

Question 45

CASE STUDY 27.11
SO YOU THOUGHT HOT DOGS WERE BAD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.11 summary
In a magazine article, three research groups reported a link between cured-meat consumption and cancer.Among 232 cases in one study, children who ate 12 or more hot dots in a month were nine times as likely as hot dog-free controls to develop leukemia.Researchers also found an increased risk for kids whose fathers ate a lot of hot dogs.Another study involving 234 cases of various childhood cancers found that children whose mothers ate hot dogs at least once a week were twice as likely as controls to develop brain tumors.The results may be due to the N-nitroso compounds in cured meats, researchers say.However, they warn that the studies are far from conclusive.

{Case study 27.11 narrative} Name one of the confounding variables in this study.

Question 46

CASE STUDY 27.11
SO YOU THOUGHT HOT DOGS WERE BAD FOR YOU?
For Questions , use the following narrative
Narrative: Case study 27.11 summary
In a magazine article, three research groups reported a link between cured-meat consumption and cancer.Among 232 cases in one study, children who ate 12 or more hot dots in a month were nine times as likely as hot dog-free controls to develop leukemia.Researchers also found an increased risk for kids whose fathers ate a lot of hot dogs.Another study involving 234 cases of various childhood cancers found that children whose mothers ate hot dogs at least once a week were twice as likely as controls to develop brain tumors.The results may be due to the N-nitroso compounds in cured meats, researchers say.However, they warn that the studies are far from conclusive.

{Case study 27.11 narrative} The studies conducted here were most likely to be of what type?

A)Prospective studies.
B)Randomized experiments.
C)Case-control studies.
D)Matched-pairs experiments.