1. Intro to Stats and Collecting Data

The age of a person is commonly considered to be a continuous random variable. Could it be considered a discrete random variable instead? Explain.

Happiness and Your Heart Is there an association between level of happiness and the risk of heart disease? Researchers studied 1739 people over a 10-year period and asked questions about their daily lives and the hassles they face. The researchers also determined which individuals in the study experienced any type of heart disease. After their analysis, they concluded that happy individuals are less likely to experience heart disease. Source: European Heart Journal 31 (9):1065–1070, February 2010.

What is the response variable? What is the explanatory variable?

"Cellolar Phones Researchers wanted to determine whether there is an association between mobile phone use and body mass index. To do so, 105,028 men and women aged 18 years or over from the United Kingdom were recruited and their cell-phone use behavior was studied (number of calls per day, number of hours per week, year cell phone was first used) along with other variables (amount of exercise, body mass index) of the individuals. The researchers found a strong positive association between duration of phone calls on a cell phone and body mass index (that is, as the duration of phone calls increases, body mass index tends to increase as well).

Many studies involving cell phones look for a link between cell-phone usage and negative health outcomes (such as stroke or cancer) due to radio-frequency exposure. The following quote is from the article: “Obesity is associated with health outcomes such as stroke and cancers, which are of interest in relation to radio frequency exposure, and therefore is potential for confounding.” Explain what this means."

"Putting It Together: Passive Smoke? The following abstract appears in The New England Journal of Medicine:BACKGROUNDThe 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.METHODSIn 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.RESULTSHousehold 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.CONCLUSIONSThe possibility of recall bias and other methodologic problems may influence the results of case-control 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.

What makes this study a case-control study? Why is this a retrospective study?"

"Putting It Together: Passive Smoke? The following abstract appears in The New England Journal of Medicine:BACKGROUNDThe 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.METHODSIn 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.RESULTSHousehold 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.CONCLUSIONSThe possibility of recall bias and other methodologic problems may influence the results of case-control 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.

Can you identify any lurking variables that may have affected this study?"

Define the following: Placebo

Define the following: Confounding

A(n) ________ design is one in which each experimental unit is randomly assigned to a treatment. A(n) ________ design is one in which the experimental units are paired up.

Grouping together similar experimental units and then randomly assigning the experimental units within each group to a treatment is called .

"[NW] Chew Your Food Researchers wanted to determine the association between number of times one chews food and food consumption. They identified 45 individuals who were 18 to 45 years of age. First, the researchers determined a baseline for number of chews before swallowing food. Next, each participant attended three sessions to eat pizza for lunch until comfortably full by chewing each portion of food 100%, 150%, and 200% of their baseline number of chews before swallowing. Food intake for each of the three chewing treatments was then measured. It was found that food consumption was reduced significantly, by 9.5% and 14.8%, respectively, for the 150% and 200% number of chews compared to the baseline. Source: Yong Zhu and James H. Hollis. “Increasing the Number of Chews before Swallowing Reduces Meal Size in Normal-Weight, Overweight, and Obese Adults,” Journal of the Academy of Nutrition and Dietetics, 11 November 2013.

What is the research objective of the study?"

"[NW] Chew Your Food Researchers wanted to determine the association between number of times one chews food and food consumption. They identified 45 individuals who were 18 to 45 years of age. First, the researchers determined a baseline for number of chews before swallowing food. Next, each participant attended three sessions to eat pizza for lunch until comfortably full by chewing each portion of food 100%, 150%, and 200% of their baseline number of chews before swallowing. Food intake for each of the three chewing treatments was then measured. It was found that food consumption was reduced significantly, by 9.5% and 14.8%, respectively, for the 150% and 200% number of chews compared to the baseline. Source: Yong Zhu and James H. Hollis. “Increasing the Number of Chews before Swallowing Reduces Meal Size in Normal-Weight, Overweight, and Obese Adults,” Journal of the Academy of Nutrition and Dietetics, 11 November 2013.

How is control used in this study?"

"Alcohol Dependence To determine if topiramate is a safe and effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this double-blind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. Source: Bankole A. Johnson, Norman Rosenthal, et al. “Topiramate for Treating Alcohol Dependence: A Randomized Controlled Trial,” Journal of the American Medical Association, 298(14):1641–1651, 2007.

What does it mean for the experiment to be placebo-controlled?"

"Alcohol Dependence To determine if topiramate is a safe and effective treatment for alcohol dependence, researchers conducted a 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this double-blind, randomized, placebo-controlled experiment, subjects were randomly given either 300 milligrams (mg) of topiramate (183 subjects) or a placebo (188 subjects) daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. Source: Bankole A. Johnson, Norman Rosenthal, et al. “Topiramate for Treating Alcohol Dependence: A Randomized Controlled Trial,” Journal of the American Medical Association, 298(14):1641–1651, 2007.

What does it mean for the experiment to be double-blind? Why do you think it is necessary for the experiment to be double-blind?"

"School Psychology A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 500 first-grade students in District 203 and randomly divides them into two groups. Group 1 is taught by means of the new method, while group 2 is taught by traditional methods. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results of the two groups are compared.

What is the response variable in this experiment?"

"School Psychology A school psychologist wants to test the effectiveness of a new method for teaching reading. She recruits 500 first-grade students in District 203 and randomly divides them into two groups. Group 1 is taught by means of the new method, while group 2 is taught by traditional methods. The same teacher is assigned to teach both groups. At the end of the year, an achievement test is administered and the results of the two groups are compared.

What type of experimental design is this?"