Exam 27: Putting What You Have Learned to the Test

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.

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?

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.

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.

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?

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?

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?

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?

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?

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?

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?

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.

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?

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.

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.

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?

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.

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?

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.

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?