chapter 4 quiz

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. The label for the dummy pill treatment should appear in the outline at the point marked "Question B." What is this label? random allocation. Finnish men. Placebo. Cancer. Vitamins.

Placebo.

Which of the following are the three principles of experimental design? Control, Randomize, Large Samples Confound, Randomize, Large Samples Confound, Randomize, Small Samples Control, Randomize, Small Samples

Control, Randomize, Large Samples

Were the extinctions that occurred in the last ice age more frequent among species of animals with large body sizes? A researcher gathers data on the average body mass (in kilograms) of all species known to have existed at that time. What are the explanatory and response variables? Explanatory: the ice age. Response: whether a species went extinct. There is no explanatory-response distinction in this situation. Explanatory: whether a species went extinct. Response: the body mass of the species. Explanatory: the ice age. Response: the body mass of a species. Explanatory: body mass of a species. Response: whether the species went extinct.

Explanatory: body mass of a species. Response: whether the species went extinct.

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. The response variable should be named in the outline at the point marked "Question C." What is this label? whether a subject took vitamins. random allocation. Whether a subject developed cancer. 29,000 Finnish men. a confidence statement.

Whether a subject developed cancer.

An observed effect that is of a size that would rarely occur by chance is called: a randomized effect. the confounding effect. a statistically significant effect. the placebo effect.

a statistically significant effect.

The most important advantage of experiments over observational studies is experiments are usually easier to carry out. we can use randomization to avoid bias in designing an experiment. a well-designed experiment can give good evidence that the treatments actually cause the response. we can study the relationship between two or more explanatory variables. an experiment can compare two or more groups.

a well-designed experiment can give good evidence that the treatments actually cause the response.

The article was headlined, "Two Cups of Coffee Can Reduce the Risk of Liver Disease, Study Finds." A meta-analysis, based on combining nine previous studies involving 430,000 individuals, concluded that consumption of two cups of coffee a day reduced the chance of cirrhosis of the liver by 44 percent; even greater consumption was found to further reduce the risk of the disease. The explanatory variable in this study is: coffee consumption. incidence of cirrhosis of the liver. not given in the quote above. There is no response variable because it is a meta-analysis.

coffee consumption.

A West Coast university statistics professor wishes to determine which surfboard brand delivers consistently longer rides, Channel Island or JS. He recruits two of his students who surf to assist in an experiment, and the student assigned to the Channel Island board is determined by coin flip. The three head out to the beach for an afternoon, with the professor holding up a sign at random times for the respective student to catch the next wave on his board, and the time spent on that wave is recorded. This is repeated until each student has ridden 10 waves. The brand of board they're riding on is not the only factor affecting the length of time they ride each wave. It is likely that the two surfing students are not identical in surfing ability. Since the professor is only interested in determining which surfboard brand delivers longer rides, the study suffers from: the placebo effect. voluntary response. convenience sampling. confounding. invalid measurement.

confounding.

The article was headlined, "Two Cups of Coffee Can Reduce the Risk of Liver Disease, Study Finds." A meta-analysis, based on combining nine previous studies involving 430,000 individuals, concluded that consumption of two cups of coffee a day reduced the chance of cirrhosis of the liver by 44 percent; even greater consumption was found to further reduce the risk of the disease. The response variable in this study is: not given in the quote above. incidence of cirrhosis of the liver. coffee consumption. There is no response variable because it is a meta-analysis.

incidence of cirrhosis of the liver.

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. The study design looked like this: An example of a confounding variable that might affect the results of this study is: the brand of cigarette smoked. the age of participant. the brand of vitamin supplement. none of the above because the subjects were divided up randomly, and any possible effects dye to confounding variables should be balanced between the two groups.

none of the above because the subjects were divided up randomly, and any possible effects dye to confounding variables should be balanced between the two groups.

Does eating while driving make an accident more likely? Researchers from the National Highway Traffic Safety Administration looked at national traffic and accident records from a recent year for those drivers who were eating versus those who were not. Result: The odds of an accident were 80 percent higher when eating than when not. This study is a(n): randomized comparative experiment. experiment, but without randomization. simple random sample. observational study, but not a simple random sample.

observational study, but not a simple random sample.

A researcher claims that the mean resting pulse rate of all college basketball players in the United States is less than the mean resting pulse rate of all professional basketball players in the United States. The resting pulse rates of a random sample of 115 college basketball players were measured as were the resting pulse rates of a random sample of 80 professional basketball players. The mean resting pulse rates of the two groups were compared. voluntary response. observational study. experiment, but without randomization. randomized comparative experiment.

observational study.

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. The method used to form the groups should appear in the outline at the point marked "Question A." What is this method? divide and conquer. First come, first served. Voluntary response. stratified sampling. random allocation.

random allocation.

A researcher studied whether meeting regularly with a weight-loss counselor helps dieters lose weight. Eighty dieters were available for the study. Half the dieters, assigned at random, received weight-loss counseling. The other half did not. After six months, the weight lost by each dieter was measured. On the average, those who met regularly with a weight-loss counselor lost more weight than those who did not. In order to create groups of subjects that should be similar, on average, in all respects, we use: lurking. confounding. randomization. All of the above.

randomization.

A researcher studied whether meeting regularly with a weight-loss counselor helps dieters lose weight. Eighty dieters were available for the study. Half the dieters, assigned at random, received weight-loss counseling. The other half did not. After six months, the weight lost by each dieter was measured. On the average, those who met regularly with a weight-loss counselor lost more weight than those who did not. This study is a(n): experiment, but without randomization. simple random sample. randomized comparative experiment. observational study, but not an SRS.

randomized comparative experiment.

Does taking large amounts of vitamins protect against cancer? To study this question, researchers enrolled 29,000 Finnish men, all smokers over the age of 50. Half of the men, selected at random, took vitamin supplements, and others took a dummy pill that has no active ingredient. The researchers followed all the men for eight years. At the end of the study, men in the vitamin group were no less likely to have cancer than men in the other group. This study cast doubt on the popular idea that taking lots of vitamins can reduce the risk of cancer. The study design looked like this: The statistical name for this study design is observational study. randomized comparative experiment. stratified random sample. simple random sample. multistage sample.

randomized comparative experiment.

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. This study is a(n): experiment, but without randomization. randomized comparative experiment. simple random sample. observational study, but not a simple random sample.

randomized comparative experiment.

An important reason for the use of randomization in designing experiments is that it tends to: reduce confounding. allow double-blinding. reduce the placebo effect. eliminate response error.

reduce confounding.

A researcher claims that the mean resting pulse rate of all college basketball players in the United States is less than the mean resting pulse rate of all professional basketball players in the United States. The resting pulse rates of a random sample of 115 college basketball players were measured as were the resting pulse rates of a random sample of 80 professional basketball players. The mean resting pulse rates of the two groups were compared. An example of a lurking variable that might affect the results of this study is: the age of the players. whether or not the players had scholarships in college. the team each player is from. the location the study was administered.

the age of the players.

A psychologist recently said that, "For relatively mild medical problems, the placebo effect will produce positive results in roughly two-thirds of patients." The placebo effect is: the bias due to voluntary response in a sample. the effect of a dummy treatment on a patient. a violation of comparative experimentation. the effect of confounding in an observational study.

the effect of a dummy treatment on a patient.

Confounding often defeats attempts to show that one variable causes changes in another variable. Confounding means that: we don't know which is the response variable and which is the explanatory variable. we would get widely varied results if we repeated the study many times. the effects of several variables are mixed up, so we cannot say which is causing the response. this was an observational study, so cause and effect conclusions are not possible.

the effects of several variables are mixed up, so we cannot say which is causing the response.

A West Coast university statistics professor wishes to determine which surfboard brand delivers consistently longer rides, Channel Island or JS. He recruits two of his students who surf to assist in an experiment, and the student assigned to the Channel Island board is determined by coin flip. The three head out to the beach for an afternoon, with the professor holding up a sign at random times for the respective student to catch the next wave on his board, and the time spent on that wave is recorded. This is repeated until each student has ridden 10 waves. The brand of surfboard in this story is: blinded. the response variable. stratified. a parameter. the explanatory variable.

the explanatory variable.

A researcher claims that the mean resting pulse rate of all college basketball players in the United States is less than the mean resting pulse rate of all professional basketball players in the United States. The resting pulse rates of a random sample of 115 college basketball players were measured as were the resting pulse rates of a random sample of 80 professional basketball players. The mean resting pulse rates of the two groups were compared. In this study, the explanatory variable is: the number of players studied in each group. the level of basketball played (college or professional) confounded with the placebo effect. the resting pulse rate.

the level of basketball played (college or professional)

A West Coast university statistics professor wishes to determine which surfboard brand delivers consistently longer rides, Channel Island or JS. He recruits two of his students who surf to assist in an experiment, and the student assigned to the Channel Island board is determined by coin flip. The three head out to the beach for an afternoon, with the professor holding up a sign at random times for the respective student to catch the next wave on his board, and the time spent on that wave is recorded. This is repeated until each student has ridden 10 waves. In the surfing story above, the time spent on the wave is: stratified. randomized. the explanatory variable. a parameter. the response variable.

the response variable.

A researcher claims that the mean resting pulse rate of all college basketball players in the United States is less than the mean resting pulse rate of all professional basketball players in the United States. The resting pulse rates of a random sample of 115 college basketball players were measured as were the resting pulse rates of a random sample of 80 professional basketball players. The mean resting pulse rates of the two groups were compared. In this study, the response variable is: the level of basketball played (college or professional) the number of players studied in each group. the resting pulse rate. confounded with the placebo effect.

the resting pulse rate.

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. An example of a lurking variable that might affect the results of this study is: whether the volunteer had a meditation session. the time of day the test was administered. whether the volunteer was being paid to participate in the study.

the time of day the test was administered.

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. In this study, the response variable is: a lurking variable. the placebo. whether the volunteer had a meditation session. the volunteer's flexibility score.

the volunteer's flexibility score.

Does eating while driving make an accident more likely? Researchers from the National Highway Traffic Safety Administration looked at national traffic and accident records from a recent year for those drivers who were eating versus those who were not. Result: The odds of an accident were 80 percent higher when eating than when not. The explanatory variable in this study is: whether the subject owned a car. the risk of an accident. whether the subject had an auto accident. whether the subject was eating.

whether the subject was eating.

Does eating while driving make an accident more likely? Researchers from the National Highway Traffic Safety Administration looked at national traffic and accident records from a recent year for those drivers who were eating versus those who were not. Result: The odds of an accident were 80 percent higher when eating than when not. An example of a lurking variable that might affect the results of this study is: whether the subject owned a cell phone. whether the subject was talking to a passenger in the car. whether the subject was eating. whether the subject had an auto accident.

whether the subject was talking to a passenger in the car.

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. In this study, the explanatory variable is: a lurking variable. the volunteer's flexibility score. the placebo. whether the volunteer had a meditation session.

whether the volunteer had a meditation session.