Exam 17: Turning Information Into Wisdom

Use the following information for questions: In a report by AP, the headline read "Even light weekend use of the party drug Ecstasy might harm intelligence, a study suggests". The headline was based on a study of 28 Ecstasy users in their mid-20s recruited off the dance floor of a nightclub. The researchers compared this group with two others of the same size, age range, and education level - one consisting of drug-free people and another of people who smoked about as much marijuana as the Ecstasy group. The researchers reported weeks after partying, those who used Ecstasy along with marijuana performed worse on intelligence tests than people who just smoked marijuana or took no drugs at all. -What was a potential confounding variable?

Use the following information for questions: A random sample of 600 students was asked whether student fees should be used to construct a new football stadium. -An additional group of 5 football players, not selected in the sample, asked to be included so that their opinions could be heard. Adding these students to the sample

Use the following information for questions: Twenty volunteers were assigned at random to one of two groups (10 people in each group). One group would take Vitamin C for two weeks, while the second group would take a placebo. At the end of the study, the proportion of colds in the two groups will be compared. -Can a conclusion that taking Vitamin C causes a change in the risk of a cold?

Use the following information for questions: A study of 42 patients with carpal tunnel syndrome (symptoms of burning numbness in the wrist to difficulty making a fist) was done ("Yoga based intervention for carpal tunnel syndrome," Garfinkel et al, JAMA 1998; 280:1601-1603). Subjects were randomly assigned to a yoga group or a control (where they were offered a wrist splint to supplement their current treatment). Results showed that subjects in the yoga group had significant improvement in grip strength, while subjects in the control group did not. -What is the response variable in the study?

Use the following information for questions: In a report by AP, the headline read "Even light weekend use of the party drug Ecstasy might harm intelligence, a study suggests". The headline was based on a study of 28 Ecstasy users in their mid-20s recruited off the dance floor of a nightclub. The researchers compared this group with two others of the same size, age range, and education level - one consisting of drug-free people and another of people who smoked about as much marijuana as the Ecstasy group. The researchers reported weeks after partying, those who used Ecstasy along with marijuana performed worse on intelligence tests than people who just smoked marijuana or took no drugs at all. -Is a conclusion that taking the drug Ecstasy causes a lower score on intelligence tests warranted?

Use the following information for questions: In a report by CNN Health News, the headlines read "Study: Junk food raises teens' risk of heart disease." The headlines were based on a study of 249 high school students between the ages of 13 and 18. One researcher said, "more than 80% of those tested were eating a diet that could promote heart disease." Ultrasound was used to measure the thickness of the carotid artery, which, the researcher said, "can be an early indicator of atherosclerosis, an abnormal hardening of the artery walls." -What was a potential confounding variable?

Write down one of the ten guiding principles summarized in Chapter 17. Give an example of the principle.

Use the following information for questions: Twenty volunteers were assigned at random to one of two groups (10 people in each group). One group would take Vitamin C for two weeks, while the second group would take a placebo. At the end of the study, the proportion of colds in the two groups will be compared. -What is the explanatory variable in the study?

Use the following information for questions: 43 sedentary adults between the ages of 50 and 76 were randomly assigned to either an exercise program four times a week for 16 weeks or they continued to be sedentary (King, et al, JAMA, January 1, 1997,pp 32-37). The exercise group slept an average of 42 minutes a night longer than the control group. -Can a conclusion that the exercise program caused more sleep?

Use the following information for questions: A random sample of 500 students showed a statistically significant relationship between where the students usually sat in class (front, middle, or back) and grade point average (GPA). -What is the response variable in the study?

Use the following information for questions: In a report by ABC News, the headlines read "City Living Increases Men's Death Risk" The headlines were based on a study of 3,617 adults who lived in the United States and were more than 25 years old. One researcher said, "Elevated levels of tumor deaths suggest the influence of physical, chemical and biological exposures in urban areas… Living in cities also involves potentially stressful levels of noise, sensory stimulation and overload, interpersonal relations and conflict, and vigilance against hazards ranging from crime to accidents." -The conservative margin of error for the sample of 3,617 adults is

Use the following information for questions: In a report by CNN Health News, the headlines read "Study: Junk food raises teens' risk of heart disease." The headlines were based on a study of 249 high school students between the ages of 13 and 18. One researcher said, "more than 80% of those tested were eating a diet that could promote heart disease." Ultrasound was used to measure the thickness of the carotid artery, which, the researcher said, "can be an early indicator of atherosclerosis, an abnormal hardening of the artery walls." -What type of study was this?

In a study for which the sample does not represent the population for the question of interest

Use the following information for questions: A study of 42 patients with carpal tunnel syndrome (symptoms of burning numbness in the wrist to difficulty making a fist) was done ("Yoga based intervention for carpal tunnel syndrome," Garfinkel et al, JAMA 1998; 280:1601-1603). Subjects were randomly assigned to a yoga group or a control (where they were offered a wrist splint to supplement their current treatment). Results showed that subjects in the yoga group had significant improvement in grip strength, while subjects in the control group did not. -Can a conclusion that yoga caused the improvement in grip strength be made?

A significance test based on a small sample may not produce a statistically significant result even if the true value differs substantially from the null value. This type of result is known as

A newspaper article reported that a large study measured the daily habits of a sample of mid-level managers. The response variable of interest was whether or not the person had a serious illness during the five years of the study. The investigators looked at 30 habits such as smoking, exercise, church attendance, and so on, and for each habit they tested the null hypothesis that the proportions with serious illness were the same for those with and without the habit. The newspaper reported, "Only one habit was significantly related to the risk of serious illness. The researchers were surprised to find that the managers who drank tea were significantly more likely to have a serious illness than managers who did not drink tea." The most likely explanation for this finding is that

Sometimes researchers are surprised to find "no effect" in a study when in fact there really is an effect in the population. This type of result is known as

Use the following information for questions: In a report by Reuters, the headline read "Emotional Support Helps Breast Cancer Survival" The headline was based on a study of 847 women (442 black women and 405 white women) with breast cancer and how they fared over a 9-year period. The authors wrote "Women in our study who reported low levels of both emotional expression and emotional support experienced 2 to 4 times greater breast cancer mortality than women reporting high levels of both". -What was a potential confounding variable?

Use the following information for questions: In a report by CNN Health News, the headlines read "Study: Junk food raises teens' risk of heart disease." The headlines were based on a study of 249 high school students between the ages of 13 and 18. One researcher said, "more than 80% of those tested were eating a diet that could promote heart disease." Ultrasound was used to measure the thickness of the carotid artery, which, the researcher said, "can be an early indicator of atherosclerosis, an abnormal hardening of the artery walls." -What was the explanatory variable?

A student doing a history project finds the ages of all of the governors of California at the time they were first elected and the ages of all the governors of Massachusetts at the time they were first elected, and then computes the mean for each state. The best way to determine if there is a difference in the mean age for the past governors of the two states is to