Exam 6: Gathering Useful Data for Examining Relationships

Use the following information for questions: A researcher wishes to see whether there is any difference in the average weight gains of athletes following one of three special diets (Diet 1, Diet 2, and Diet 3). The initial study design was to randomly assign the athletes to one of the three diet groups and place them on the diet for six weeks. The weight gain (in pounds) at the end of the six weeks would be recorded for each athlete. -Suppose that 80% of the athletes are men and 20% of the athletes are women. In a randomized design it is possible that a diet (treatment) could have very few or no female athletes assigned to it. Suggest a way to improve on the design for the next study so as to control for the possible effects of gender.

Use the following information for questions: An observational study has found that drivers who report that they routinely wear a seatbelt were less likely to have been given a traffic ticket for speeding in the past three years. -A politician hears about this result and proposes a bill to finance a public education campaign to get people to wear seatbelts. He argues that if it works, it would reduce speeding as well. What would you conclude about his reasoning?

A case-control study found higher exposure to gases, dusts, and fumes in the workplace among patients with bronchitis (an inflammation of the lungs) than among patients without bronchitis. What type of study is this?

A researcher randomly sampled 100 students at a university and asked them if they regularly take vitamins. He also asked them how many colds they had in the last six months. He then compared the number of colds experienced by those who take vitamins to the number of colds experienced by those who don't take vitamins. What type of study is this?

Use the following information for questions: Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly blacks. To investigate whether drug A can reduce the pain associated with sickle-cell disease, a study by the National Institutes of Health randomly assigned 150 sickle-cell sufferers to receive the drug. Placebos were given to another 150 sickle-cell sufferers. Great care was used to ensure that the 300 participants did not know if their pill contained the drug. At the end of the treatment period, the researchers counted the number of episodes of pain reported by each subject. -What is the response variable in this study?

Use the following information for questions: Researchers would like to compare meditation and exercise to see which is more effective for reducing stress. One hundred people who suffer from high stress volunteer to participate in a study for ten weeks. Participants will either be given a 10-week course in meditation or will participate in a 10-week exercise program. The researchers must decide whether to randomly assign the volunteers to the two programs, or allow them to choose. -Which of the following is the main advantage of randomly assigning participants to the two programs rather than allowing them to choose?

Explain which of the "difficulties and disasters" is most likely to be a problem in the following observational study and explain why. Successful female social workers and engineers were asked to recall whether they had any female professors in college who were particularly influential in their choice of career. More of the engineers than the social workers recalled a female professor who stood out in their minds.

A group of 709 patients with lung cancer was compared to a group of 709 controls. For each patient with lung cancer, a control patient from the same hospital and the same sex and age as the lung cancer patient was selected. The two groups were compared on their smoking habits. Which of the following applies to this study?

Use the following information for questions: A study of changing speed limits in the United States finds no evidence that higher limits fuel more deaths. A scientist examined shifts in speed limit laws over the past few decades. Highway speed limits were initially throttled in the 1970s in response to the gas shortage. In the 1980s the focus shifted to public safety. Yet in 1995, Congress returned all speed limit authority back to the states, and many states raised their top highway speeds. While limits ranged from 75 mph to 55 and back again, no significant increase in fatalities per mile driven are evident. In fact, from 1968 to 1991, the fatality rate per 100 million miles declined by 63.2 percent. The scientist attributes the decrease to safer cars, increased use of seat belts, an increase in the minimum legal drinking age, and better road maintenance. "Automobile safety features and enforcement emerge as important factors in increasing highway safety,"the scientist contends. "Speed limits are far less important." -What type of study is described above?

A researcher conducts a study to determine whether or not taking Vitamin C prevents colds. What is the explanatory variable in this study?

Use the following information for questions: Decide if the study is an observational study or an experiment. -Twenty blue-fin tuna were randomly assigned to two tanks of water, 10 tuna in each tank. One tank was polluted with methyl mercury, while the other tank was not polluted. The survival times of the fish in the two tanks were compared.

You wish to study the effect of a tutoring program to help improve student grades in an introductory statistics course. Propose a retrospective study design to answer the question.

Use the following information for questions: Having a coffee fix just before a workout may not be the best idea, a study suggests. Researchers in Switzerland found that the amount of caffeine in just two cups of coffee limits the body's ability to increase blood flow to the heart during exercise. The study included 18 young, healthy people who were regular coffee drinkers. They did not drink any coffee for 36 hours prior to study testing. The researchers used high-tech PET scans to measure the participants' heart blood flow before and after they rode a stationary bike and then repeated the testing procedure after swallowing a tablet containing 200 milligrams of caffeine -- the amount contained in two cups of coffee. The caffeine did not affect heart blood flow when the participants were inactive. However, measurements taken immediately after exercise showed a slowdown in heart blood flow after they'd taken the caffeine tablets, compared to their previous results. -Which variable is the response variable in this study?

Use the following information for questions: A researcher asked random samples of 50 kindergarten teachers and 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level. -In this study, it turns out that 12^th grade teachers generally earn more money than kindergarten teachers. The variable 'income of the teacher' is an example of

Use the following information for questions: For each relationship (conclusions from one or more studies), define what the response and explanatory variables are. -College instructors with a Ph.D. degree earn, on average, more than college instructors with only a Master's degree.

Use the following information for questions: For each relationship (conclusions from one or more studies), define what the response and explanatory variables are. -The average life expectancy in Russia dropped from 64 years (1991) to 57 years (1995). One theory was that radiation from nuclear fallout was responsible.

Use the following information for questions: For each relationship (conclusions from one or more studies), define what the response and explanatory variables are. -Course grades based on student evaluations varied across the various fields. Social science courses generally received higher scores than natural science courses.

An observational study is done to see if eating at least two apples a week helps prevent tooth decay in children. However, the researchers are aware that children who eat apples may also drink less soda, so they measure soda consumption as well. In this example, soda consumption is an example of

Use the following information for questions: A difficult birth or a history of mental illness in a parent may put a baby at greater risk for autism. The Centers for Disease Control and Prevention said that in a study of 698 Danish children with the developmental disorder, researchers found a disproportionately high number had been born before the 35th week of pregnancy, had suffered from low birth weights and were in a breech position at birth. The children, all of whom were born after 1972 and diagnosed with autism before 2000, also were more likely to have a parent who had been diagnosed with schizophrenia-like psychosis before the autism was discovered. -Which of the following applies to this study?

What is the most likely problem for a randomized experiment that uses volunteers?