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. In the study safer cars, increased use of seat belts, an increase in the minimum legal drinking age, and better road maintenance are mentioned as reasons for a decline in the fatality rate between 1968 and 1991 . What do we call these 4 variables?
a. Response variables
b. Qualitative variables
c. Confounding variables
d. Interacting variables
Q. 2A 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. Prospective observational, because we already know that the speed limits were changed at the beginning of the study. We have to wait and see if the fatality rate has changed.
b. Retrospective observational, because records were studied going all the way back to the 1970's.
c. An experiment, people have to actively drive their cars at these different speed limits.
Q. 3An 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. It is correct.
b. It is not correct because the relationship between seatbelt use and speeding tickets is probably due to confounding variables.
c. It is not correct because the cause and effect relationship is most likely in the other direction.
d. It is not correct because the results of an observational study cannot be extended to a population.
Q. 4An 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. Of the following, which is the most likely explanation for this observed relationship?
a. Police are less likely to stop a driver for speeding when they can see that he or she is wearing a seatbelt.
b. People are less likely to speed when they are wearing a seatbelt.
c. Confounding variables such as age and attention to risk factors in driving cause the same drivers who are likely to wear seatbelts to also be less likely to speed.
d. Relying on memory has created a problem because most people don't remember if they have had a speeding ticket in the past three years.
Q. 5Researchers 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. Suppose participants are randomly assigned to the two programs and a psychologist measures their stress levels before and after the 10-week program, without being told who is in which program. This experiment would be
a. Single blind as long as the participants are not told the results of the stress level measurements.
b. Single blind because the psychologist doesn't know who is in which program, but the participants do know.
c. Double blind as long as the participants are not told the results of the stress level measurements.
d. Neither single nor double blind.
Q. 6Researchers 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 an advantage of allowing participants to choose the program in which to participate?
a. Allowing them to choose will increase the ecological validity of the study because in the real world people choose their own programs.
b. Confounding variables, such as past practice of meditation, should be approximately equal for the two groups.
c. Allowing participants to choose will allow the results to be extended to the population of all adults.
d. If participants are allowed to choose then a cause and effect conclusion can be made.
Q. 7Researchers 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?
a. The participants are more likely to stick with the program for the full 10 weeks.
b. Confounding variables, such as past practice of meditation, should be approximately equal for the two groups.
c. Random assignment ensures that the two sample sizes are equal and that requirement is necessary in studies like this one.
d. Random assignment will allow the results to be extended to the population of all adults.
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