Television in the Bedroom Researchers Christelle Delmas and associates wanted to

Problem 1E In your own words, define explanatory variable and response variable.

Problem 2E What is an observational study? What is a designed experiment? Which allows the researcher to claim causation between an explanatory variable and a response variable?

Problem 4E Given a choice, would you conduct a study using an observational study or a designed experiment? Why?

Problem 5E What is a cross-sectional study? What is a case-control study? Which is the superior observational study? Why?

Problem 7E Explain why it would be unlikely to use a designed experiment to answer the research question posed in Example. Researchers wanted to determine the long-term benefits of the influenza vaccine on seniors aged 65 years and older. The researchers looked at records of over 36,000 seniors for 10 years. The seniors were divided into two groups. Group 1 were seniors who chose to get a flu vaccination shot, and group 2 were seniors who chose not to get a flu vaccination shot. After observing the seniors for 10 years, it was determined that seniors who get flu shots are 27% less likely to be hospitalized for pneumonia or influenza and 48% less likely to die from pneumonia or influenza. (Source: Kristin L. Nichol, MD, MPH, MBA, James D. Nordin, MD, MPH, David B. Nelson, PhD, John P. Mullooly, PhD, Eelko Hak, PhD. “Effectiveness of Influenza Vaccine in the Community-Dwelling Elderly,” New England Journal of Medicine 357:1373–1381, 2007)

Problem 8E What does it mean when an observational study is retrospective? What does it mean when an observational study is prospective?

Problem 3E Explain what is meant by confounding. What is a lurking variable?

Problem 9E In Problems, determine whether the study depicts an observational study or an experiment. Researchers wanted to know if there is a link between proximity to high-tension wires and the rate of leukemia in children. To conduct the study, researchers compared the rate of leukemia for children who lived within 1/2 mile of high-tension wires to the rate of leukemia for children who did not live within 1/2 mile of high-tension wires.

Problem 10E In Problems, determine whether the study depicts an observational study or an experiment. Rats with cancer are divided into two groups. One group receives 5 milligrams (mg) of a medication that is thought to fight cancer, and the other receives 10 mg. After 2 years, the spread of the cancer is measured.

Problem 11E In Problems, determine whether the study depicts an observational study or an experiment. Seventh-grade students are randomly divided into two groups. One group is taught math using traditional techniques; the other is taught math using a reform method. After 1 year, each group is given an achievement test to compare proficiency.

Problem 6E The data used in the influenza study presented in Example were obtained from a cohort study. What does this mean? Why is a cohort study superior to a case-control study?

Problem 14E In Problems, determine whether the study depicts an observational study or an experiment. While shopping, 200 people are asked to perform a taste test in which they drink from two randomly placed, unmarked cups. They are then asked which drink they prefer.

Problem 13E In Problems, determine whether the study depicts an observational study or an experiment. A survey is conducted asking 400 people, “Do you prefer Coke or Pepsi?”

Problem 12E In Problems, determine whether the study depicts an observational study or an experiment. A poll is conducted in which 500 people are asked whom they plan to vote for in the upcoming election.

Problem 16E In Problems, determine whether the study depicts an observational study or an experiment. Conservation agents netted 250 large-mouth bass in a lake and determined how many were carrying parasites.

Problem 15E In Problems, determine whether the study depicts an observational study or an experiment. Sixty patients with carpal tunnel syndrome are randomly divided into two groups. One group is treated weekly with both acupuncture and an exercise regimen. The other is treated weekly with the exact same exercise regimen, but no acupuncture. After 1 year, both groups are questioned about their level of pain due to carpal tunnel syndrome.

Problem 18E Daily Coffee Consumption Researchers wanted to determine if there was an association between daily coffee consumption and the occurrence of skin cancer. The researchers looked at 93,676 women enrolled in the Women’s Health Initiative Observational Study and asked them to report their coffee-drinking habits. The researchers also determined which of the women had nonmelanoma skin cancer. After their analysis, the researchers concluded that consumption of six or more cups of caffeinated coffee per day was associated with a reduction in nonmelanoma skin cancer. Source: European Journal of Cancer Prevention, 16(5): 446–452, October 2007 (a) What type of observational study was this? Explain. ________________ (b) What is the response variable in the study? What is the explanatory variable? ________________ (c) In their report, the researchers stated that “After adjusting for various demographic and lifestyle variables, daily consumption of six or more cups was associated with a 30% reduced prevalence of nonmelanoma skin cancer.” Why was it important to adjust for these variables?

Problem 17E Happiness and Your Heart Researchers wanted to determine if there was an association between the level of happiness of an individual and their risk of heart disease. The researchers studied1739 people over the course of 10 years. During this 10-year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of heart disease over the 10-year period. After their analysis, the researchers concluded that the happy individuals were less likely to experience heart disease. Source: European Heart Journal31 (9):1065–1070, February 2010. (a) What type of observational study is this? Explain. ________________ (b) What is the response variable? What is the explanatory variable? ________________ (c) In the report, the researchers stated that “the research team also hasn’t ruled out that a common factor like genetics could be causing both the emotions and the heart disease.” Use the language introduced in this section to explain what this sentence means.

Problem 19E Television in the Bedroom Researchers Christelle Delmas and associates wanted to determine if having a television (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 379 twelve-year-old French adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Source: Christelle Delmas, Carine Platat, Brigette Schweitzer, Aline Wagner, Mohamed Oujaa, and Chantal Simon. “Association Between Television in Bedroom and Adiposity Throughout Adolescence,” Obesity, 15:2495–2503, 2007 (a) Why is this an observational study? What type of observational study is this? ________________ (b) What is the response variable in the study? What is the explanatory variable? ________________ (c) Can you think of any lurking variables that may affect the results of the study? ________________ (d) In the report, the researchers stated, “These results remain significant after adjustment for socioeconomic status.” What does this mean? ________________ (e) Can we conclude that a television in the bedroom causes a higher body mass index? Explain.

Problem 21E Analyze the Article Write a summary of the following opinion. The opinion was posted at abcnews.com. Include the type of study conducted, possible lurking variables, and conclusions. What is the message of the author of the article?

Problem 20E Get Married, Gain Weight Researcher Penny Gordon-Larson and her associate wanted to determine whether young couples who marry or cohabitate are more likely to gain weight than those who stay single. The researchers followed 8000 men and women for 7 years as they matured from teens to young adults. When the study began, none of the participants were married or living with a romantic partner. By the end of the study, 14% of the participants were married and 16% were living with a romantic partner. The researchers found that married or cohabiting women gained, on average, 9 pounds more than single women, and married or cohabiting men gained, on average, 6 pounds more than single men. (a) Why is this an observational study? What type of observational study is this? ________________ (b) What is the response variable in the study? What is the explanatory variable? ________________ (c) Identify some potential lurking variables in this study. ________________ (d) Can we conclude that getting married or cohabiting causes one to gain weight? Explain.

Problem 22E Reread the article in Problem from Section. What type of observational study does this appear to be? Name some lurking variables that the researchers accounted for. Reference Article: Study: Educational TV for Toddlers OK CHICAGO (AP)—Arthur and Barney are OK for toddler TV-watching, but not Rugrats and certainly not Power Rangers, reports a new study of early TV-watching and future attention problems. The research involved children younger than 3, so TV is mostly a no–no anyway, according to the experts. But if TV is allowed, it should be of the educational variety, the researchers said. Every hour per day that kids under 3 watched violent child-oriented entertainment their risk doubled for attention problems five years later, the study found. Even nonviolent kids’ shows like Rugrats and The Flintstones carried a still substantial risk for attention problems, though slightly lower. On the other hand, educational shows, including Arthur, Barney and Sesame Street had no association with future attention problems. Interestingly, the risks only occurred in children younger than age 3, perhaps because that is a particularly crucial period of brain development. Those results echo a different study last month that suggested TV-watching has less impact on older children’s behavior than on toddlers. The American Academy of Pediatrics recommends no television for children younger than 2 and limited TV for older children. The current study by University of Washington researchers was prepared for release Monday in November’s issue of the journal Pediatrics. Previous research and news reports on TV’s effects have tended to view television as a single entity, without regard to content. But “the reality is that it’s not inherently good or bad. It really depends on what they watch,” said Dr. Dimitri Christakis, who co-authored the study with researcher Frederick Zimmerman. Their study was based on parent questionnaires. They acknowledge it’s observational data that only suggests a link and isn’t proof that TV habits cause attention problems. Still, they think the connection is plausible. The researchers called a show violent if it involved fighting, hitting people, threats or other violence that was central to the plot or a main character. Shows listed included Power Rangers, Lion King and Scooby Doo. These shows, and other kids’ shows without violence, also tend to be very fast-paced, which may hamper children’s ability to focus attention, Christakis said. Shows with violence also send a flawed message, namely that “if someone gets bonked on the head with a rolling pin, it just makes a funny sound and someone gets dizzy for a minute and then everything is back to normal,” Christakis said. Dennis Wharton of the National Association of Broadcasters, a trade association for stations and networks including those with entertainment and educational children’s TV shows, said he had not had a chance to thoroughly review the research and declined to comment on specifics. Wharton said his group believes “there are many superb television programs for children, and would acknowledge that it is important for parents to supervise the media consumption habits of young children.” The study involved a nationally representative sample of 967 children whose parents answered governmentfunded child development questionnaires in 1997 and 2002. Questions involved television viewing habits in 1997. Parents were asked in 2002 about their children’s behavior, including inattentiveness, difficulty concentrating and restlessness. The researchers took into account other factors that might have influenced the results—including cultural differences and parents’ education levels—and still found a strong link between the non-educational shows and future attention problems. Peggy O’Brien, senior vice president for educational programming and services at the Corporation for Public Broadcasting, said violence in ads accompanying shows on commercial TV might contribute to the study results. She said lots of research about brain development goes into the production of educational TV programming for children, and that the slower pace is intentional. “We want it to be kind of an extension of play” rather than fantasy, she said. Source: “Study: Educational TV for Toddlers OK” by Chicago (AP), © 2008. Reprinted with permission by The Associated Press.

Problem 23E Putting It Together: Passive Smoke? The following abstract appears in The New England Journal of Medicine: BACKGROUND. The relation between passive smoking and lung cancer is of great public health importance. Some previous studies have suggested that exposure to environmental tobacco smoke in the household can cause lung cancer, but others have found no effect. Smoking by the spouse has been the most commonly used measure of this exposure. METHODS. In order to determine whether lung cancer is associated with exposure to tobacco smoke within the household, we conducted a case-control study of 191 patients with lung cancer who had never smoked and an equal number of persons without lung cancer who had never smoked. Lifetime residential histories including information on exposure to environmental tobacco smoke were compiled and analyzed. Exposure was measured in terms of “smoker-years,” determined by multiplying the number of years in each residence by the number of smokers in the household. RESULTS. Household exposure to 25 or more smoker-years during childhood and adolescence doubled the risk of lung cancer. Approximately 15 percent of the control subjects who had never smoked reported this level of exposure. Household exposure of less than 25 smoker-years during childhood and adolescence did not increase the risk of lung cancer. Exposure to a spouse’s smoking, which constituted less than one third of total household exposure on average, was not associated with an increase in risk. CONCLUSIONS. The possibility of recall bias and other methodologic problems may influence the results of casecontrol studies of environmental tobacco smoke. Nonetheless, our findings regarding exposure during early life suggest that approximately 17 percent of lung cancers among nonsmokers can be attributed to high levels of exposure to cigarette smoke during childhood and adolescence. (a) What is the research objective? ________________ (b) What makes this study a case-control study? Why is this a retrospective study? ________________ (c) What is the response variable in the study? Is it qualitative or quantitative? ________________ (d) What is the explanatory variable in the study? Is it qualitative or quantitative? ________________ (e) Can you identify any lurking variables that may have affected this study? ________________ (f ) What is the conclusion of the study? Can we conclude that exposure to smoke in the household causes lung cancer? ________________ (g) Would it be possible to design an experiment to answer the research question in part (a)? Explain.

In your own words, define explanatory variable and response variable.

What is an observational study? What is a designed experiment? Which allows the researcher to claim causation between an explanatory variable and a response variable?

Explain what is meant by confounding. What is a lurking variable?

Given a choice, would you conduct a study using an observational study or a designed experiment? Why?

What is a cross-sectional study? What is a case-control study? Which is the superior observational study? Why?

The data used in the influenza study presented in Example 3 were obtained from a cohort study. What does this mean? Why is a cohort study superior to a case-control study?

Explain why it would be unlikely to use a designed experiment to answer the research question posed in Example 3.

What does it mean when an observational study is retrospective? What does it mean when an observational study is prospective?

In Problems 916, determine whether the study depicts an observational study or an experiment. Researchers wanted to know if there is a link between proximity to high-tension wires and the rate of leukemia in children. To conduct the study, researchers compared the rate of leukemia for children who lived within 1 2 mile of high-tension wires to the rate of leukemia for children who did not live within 1 2 mile of high-tension wires.

In Problems 916, determine whether the study depicts an observational study or an experiment. Rats with cancer are divided into two groups. One group receives 5 milligrams (mg) of a medication that is thought to fight cancer, and the other receives 10 mg. After 2 years, the spread of the cancer is measured.

In Problems 916, determine whether the study depicts an observational study or an experiment.Seventh-grade students are randomly divided into two groups. One group is taught math using traditional techniques; the other is taught math using a reform method. After 1 year, each group is given an achievement test to compare proficiency.

In Problems 916, determine whether the study depicts an observational study or an experiment.A poll is conducted in which 500 people are asked whom they plan to vote for in the upcoming election.

In Problems 916, determine whether the study depicts an observational study or an experiment.A survey is conducted asking 400 people, Do you prefer Coke or Pepsi?

In Problems 916, determine whether the study depicts an observational study or an experiment.While shopping, 200 people are asked to perform a taste test in which they drink from two randomly placed, unmarked cups. They are then asked which drink they prefer.

In Problems 916, determine whether the study depicts an observational study or an experiment.Sixty patients with carpal tunnel syndrome are randomly divided into two groups. One group is treated weekly with both acupuncture and an exercise regimen. The other is treated weekly with the exact same exercise regimen, but no acupuncture. After 1 year, both groups are questioned about their level of pain due to carpal tunnel syndrome.

In Problems 916, determine whether the study depicts an observational study or an experiment.Conservation agents netted 250 large-mouth bass in a lake and determined how many were carrying parasites.

Happiness and Your Heart Researchers wanted to determine if there was an association between the level of happiness of an individual and their risk of heart disease. The researchers studied 1739 people over the course of 10 years. During this 10-year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of heart disease over the 10-year period. After their analysis, the researchers concluded that the happy individuals were less likely to experience heart disease. Source: European Heart Journal 31 (9):10651070, February 2010. (a) What type of observational study is this? Explain. (b) What is the response variable? What is the explanatory variable? (c) In the report, the researchers stated that the research team also hasnt ruled out that a common factor like genetics could be causing both the emotions and the heart disease. Use the language introduced in this section to explain what this sentence means.

Daily Coffee Consumption Researchers wanted to determine if there was an association between daily coffee consumption and the occurrence of skin cancer. The researchers looked at 93,676 women enrolled in the Womens Health Initiative Observational Study and asked them to report their coffee-drinking habits. The researchers also determined which of the women had nonmelanoma skin cancer. After their analysis, the researchers concluded that consumption of six or more cups of caffeinated coffee per day was associated with a reduction in nonmelanoma skin cancer. Source: European Journal of Cancer Prevention, 16(5): 446 452, October 2007 (a) What type of observational study was this? Explain. (b) What is the response variable in the study? What is the explanatory variable? (c) In their report, the researchers stated that After adjusting for various demographic and lifestyle variables, daily consumption of six or more cups was associated with a 30% reduced prevalence of nonmelanoma skin cancer. Why was it important to adjust for these variables?

Television in the Bedroom Researchers Christelle Delmas and associates wanted to determine if having a television (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 379 twelve-year-old French adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Source: Christelle Delmas, Carine Platat, Brigette Schweitzer, Aline Wagner, Mohamed Oujaa, and Chantal Simon. Association Between Television in Bedroom and Adiposity Throughout Adolescence, Obesity, 15:24952503, 2007 (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? What is the explanatory variable? (c) Can you think of any lurking variables that may affect the results of the study? (d) In the report, the researchers stated, These results remain significant after adjustment for socioeconomic status. What does this mean? (e) Can we conclude that a television in the bedroom causes a higher body mass index? Explain.

Television in the Bedroom Researchers Christelle Delmas and associates wanted to determine if having a television (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 379 twelve-year-old French adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Source: Christelle Delmas, Carine Platat, Brigette Schweitzer, Aline Wagner, Mohamed Oujaa, and Chantal Simon. Association Between Television in Bedroom and Adiposity Throughout Adolescence, Obesity, 15:24952503, 2007 (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? What is the explanatory variable? (c) Can you think of any lurking variables that may affect the results of the study? (d) In the report, the researchers stated, These results remain significant after adjustment for socioeconomic status. What does this mean? (e) Can we conclude that a television in the bedroom causes a higher body mass index? Explain.women, and married or cohabiting men gained, on average, 6 pounds more than single men. (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? What is the explanatory variable? (c) Identify some potential lurking variables in this study. (d) Can we conclude that getting married or cohabiting causes one to gain weight? Explain.

Analyze the Article Write a summary of the following opinion. The opinion was posted at abcnews.com. Include the type of study conducted, possible lurking variables, and conclusions. What is the message of the author of the article? Power Lines and CancerTo Move or Not to Move New Research May Cause More Fear Than Warranted, One Physician Explains OPINION by JOSEPH MOORE, M.D. A recent study out of Switzerland indicates there might be an increased risk of certain blood cancers in people with prolonged exposure to electromagnetic fields, like those generated from high-voltage power lines. If you live in a house near one of these high-voltage power lines, a study like this one might make you wonder whether you should move. But based on what we know now, I dont think thats necessary. We can never say there is no risk, but we can say that the risk appears to be extremely small. Scare Science The results of studies like this add a bit more to our knowledge of potential harmful environmental exposures, but they should also be seen in conjunction with the results of hundreds of studies that have gone before. It cannot be seen as a definitive call to action in and of itself. The current study followed more than 20,000 Swiss railway workers over a period of 30 years. True, that represents a lot of people over a long period of time. However, the problem with many epidemiological studies, like this one, is that it is difficult to have an absolute control group of people to compare results with. The researchers compared the incidence of different cancers of workers with a high amount of electromagnetic field exposure to those workers with lower exposures. These studies arent like those that have identified definitive links between an exposure and a disease like those involving smoking and lung cancer. In those studies, we can actually measure the damage done to lung tissue as a direct result of smoking. But usually its very difficult for the conclusions of an epidemiological study to rise to the level of controlled studies in determining public policy. Remember the recent scare about coffee and increased risk of pancreatic cancer? Or the alwayssimmering issue of cell phone use and brain tumors? As far as I can tell, none of us have turned in our cell phones. In our own minds, weve decided that any links to cell phone use and brain cancer have not been proven definitively. While we cant say that there is absolutely no risk in using cell phones, individuals have determined on their own that the potential risks appear to be quite small and are outweighed by the benefits. Findings Shouldnt Lead to Fear As a society, we should continue to investigate these and other related exposures to try to prove one way or another whether they are disease-causing. If we dont continue to study, we wont find out. Its that simple. When findings like these come out, and Im sure there will be more in the future, I would advise people not to lose their heads. Remain calm. You should take the results as we scientists doas intriguing pieces of data about a problem we will eventually learn more about, either positively or negatively, in the future. It should not necessarily alter what we do right now. What we can do is take actions that we know will reduce our chances of developing cancer. Stop smoking and avoid passive smoke. It is the leading cause of cancer that individuals have control over. Whenever you go outside, put on sunscreen or cover up. Eat a healthy diet and stay physically active. Make sure you get tested or screened. Procedures like colonoscopies, mammograms, pap smears and prostate exams can catch the early signs of cancer, when the chances of successfully treating them are the best. Taking the actions above will go much farther in reducing your risks for cancer than moving away from power lines or throwing away your cell phone. Dr. Joseph Moore is a medical oncologist at Duke University Comprehensive Cancer Center. Source: Reprinted with the permission of the author.

Reread the article in Problem 55 from Section 1.1. What type of observational study does this appear to be? Name some lurking variables that the researchers accounted for.

Putting It Together: Passive Smoke? The following abstract appears in The New England Journal of Medicine: BACKGROUND. The relation between passive smoking and lung cancer is of great public health importance. Some previous studies have suggested that exposure to environmental tobacco smoke in the household can cause lung cancer, but others have found no effect. Smoking by the spouse has been the most commonly used measure of this exposure. METHODS. In order to determine whether lung cancer is associated with exposure to tobacco smoke within the household, we conducted a case-control study of 191 patients with lung cancer who had never smoked and an equal number of persons without lung cancer who had never smoked. Lifetime residential histories including information on exposure to environmental tobacco smoke were compiled and analyzed. Exposure was measured in terms of smoker-years, determined by multiplying the number of years in each residence by the number of smokers in the household. RESULTS. Household exposure to 25 or more smoker-years during childhood and adolescence doubled the risk of lung cancer. Approximately 15 percent of the control subjects who had never smoked reported this level of exposure. Household exposure of less than 25 smoker-years during childhood and adolescence did not increase the risk of lung cancer. Exposure to a spouses smoking, which constituted less than one third of total household exposure on average, was not associated with an increase in risk. CONCLUSIONS. The possibility of recall bias and other methodologic problems may influence the results of casecontrol studies of environmental tobacco smoke. Nonetheless, our findings regarding exposure during early life suggest that approximately 17 percent of lung cancers among nonsmokers can be attributed to high levels of exposure to cigarette smoke during childhood and adolescence. (a) What is the research objective? (b) What makes this study a case-control study? Why is this a retrospective study? (c) What is the response variable in the study? Is it qualitative or quantitative? (d) What is the explanatory variable in the study? Is it qualitative or quantitative? (e) Can you identify any lurking variables that may have affected this study? (f ) What is the conclusion of the study? Can we conclude that exposure to smoke in the household causes lung cancer? (g) Would it be possible to design an experiment to answer the research question in part (a)? Explain.