Question 1

Rolando realizes that whenever he studies for at least two hours immediately before a physics exam, he gets an A on the exam, but when he does not study immediately before an exam, he gets no higher than a C on the exam. He concludes that the time spent studying immediately before the exams is responsible for his improved grades. Rolando is

Accepted Answer

Rolando's observation of his grades improving when he studies immediately before an exam and not doing as well when he doesn't study suggests a direct correlation between his study habits and his exam performance. This makes it very probable that his conclusion about the causation (studying leading to better grades) is correct.

Question 2

Tatiana observes that all of her friends who have more than five tattoos also have more than five body piercings, and concludes that getting multiple tattoos makes people also get multiple piercings. Tatiana is

Accepted Answer

Tatiana is observing a correlation (a relationship) between having more than five tattoos and having more than five body piercings but is mistakenly inferring that one causes the other without evidence for a causal link, which is a common error known as confusing correlation with causation.

Question 3

A research project is conducted by offering a randomly selected 300 of the 500 local Toyota Prius owners a chance to use a new fuel additive for 6 months to see if their gas mileage improves. 225 of the 300 randomly selected Prius owners agree to the offer, 50 of those drop out of the project after 1 month, another 50 drop out after 2 months, and 25 more drop out after 3 months. The rest remain for the duration of the project. Using the intention to treat method, the results from how many of the Prius owners who were randomly selected should be included in the research project?

Accepted Answer

The intention to treat method includes all participants who were originally allocated to each group, regardless of whether they completed the study, adhered to the intervention, or were lost to follow-up. Therefore, all 300 randomly selected Prius owners should be included in the analysis.

Question 4

Ravi notices that all of his neighbors who own cats are also divorced, and concludes that cat ownership must result in divorce. Ravi is

Accepted Answer

Ravi is confusing correlation (the relationship between cat ownership and divorce among his neighbors) with causation (the idea that one causes the other). Just because two things occur together does not mean one causes the other.

Question 5

A research project is conducted by offering a randomly selected 300 of the 500 local Toyota Prius owners a chance to use a new fuel additive for 6 months to see if their gas mileage improves. 225 of the 300 randomly selected Prius owners agree to the offer, 50 of those drop out of the project after 1 month, another 50 drop out after 2 months, and 25 more drop out after 3 months. The rest remain for the duration of the project. Using the intention to treat method, the results from how many of the Prius owners who were not selected to be a part of the project should be included in the research project?

Accepted Answer

The intention to treat method includes all participants who were originally allocated to each group, regardless of whether they completed the study. Since 300 were selected and 200 were not part of the study, the results from the 200 not selected should be included to maintain the integrity of the original random assignment.

Question 6

Clarissa notices that her satellite TV signal becomes scrambled whenever there is a major thunderstorm in her area. She concludes that the scrambled satellite signal must be causing the severe thunderstorms. Clarissa is

Accepted Answer

Severe thunderstorms can disrupt satellite signals, so the causation is likely in the opposite direction: the thunderstorms cause the scrambled signal, not the other way around.

Question 7

Daniel notices that every year with a mild winter, his roses begin to bloom in February, but every year with a severe winter, his roses do not begin to bloom until April. He concludes that the severity of the winter is responsible for the month in which his roses begin to bloom. Daniel is

Accepted Answer

Daniel's observation of the timing of his roses' blooming in relation to the severity of the winter suggests a causal relationship, where the severity of the winter influences the blooming time. This is a reasonable conclusion based on the observed pattern.

Question 8

A procedure in which two groups are compared based on whether they were part of an initially specified random sample subjected to an experimental protocol is called

Accepted Answer

Intention to treat is a strategy in randomized controlled trials where participants are analyzed in the groups to which they were originally assigned, regardless of whether they completed the intervention according to the protocol or not. This approach helps to preserve the benefits of randomization, thus providing a more accurate reflection of the intervention's effectiveness in real-world conditions.

Question 9

Suppose that a study is released stating that the more time a person spends fishing, the smaller the chance that the person is a vegetarian. This is best described as an example of

Accepted Answer

This is an example of a negative correlation because as the time spent fishing increases, the likelihood of being a vegetarian decreases. Negative correlation indicates that as one variable increases, the other decreases.

Question 10

Identifying the causal effects of a policy by looking at two samples that lie on either side of a threshold is called

Accepted Answer

Regression discontinuity design is a quasi-experimental pretest-posttest design that allows researchers to estimate a causal effect of an intervention by assigning a cutoff or threshold above or below which an intervention is assigned, and then comparing outcomes on either side of that cutoff.

Question 11

Refer to the information provided in Scenario 22.3 below to answer the question(s) that follow.
SCENARIO 22.3: Consider a local high school that has 300 sophomores considered to be at-risk students. A privately-sponsored after-school sports program has been established to try to help at-risk students succeed in finishing high school. The local government wants to know if this program reduces the students' probability of dropping out of high school before the end of their junior year, and decides to randomly sample 150 of the 300 at-risk sophomores and invite them to attend the after-school program at no cost. 100 students accept the invitation, and by the end of their junior year, the drop-out percentage of the 100 students who attended the program was lower than the drop-out percentage of the 200 students who did not attend the program.
-Refer to Scenario 22.3. Based on the information in the scenario, can you conclude that the after-school program had a positive effect?

Accepted Answer

The 100 students who accepted the offer to attend the program may have had different motivations or characteristics compared to those who did not accept, making them a non-random subset of the 150 students offered the program. This selection bias prevents a clear conclusion about the program's effectiveness based solely on the observed outcomes.

Question 12

A research project is conducted by offering a randomly selected 75 of the 200 local dog owners a chance to have their dogs wear a new flea collar for three months to see if the collar reduces the incidence of fleas. 50 of the 75 randomly selected dog owners agree to the offer, and 25 of those drop out of the study before the end of the three months. Using the intention to treat method, the results from how many of the dogs that were not selected to be a part of the project should be included in the research project?

Accepted Answer

The answer of A research project is conducted by offering...

Question 13

Bethany notices that whenever she receives a text message, her roommate Stella is playing her tuba. She concludes that Stella's tuba playing is causing her to receive text messages. Bethany is

Accepted Answer

The answer of Bethany notices that whenever she receives a...

Question 14

Suppose that a study is released stating that as people increase the number of times they brush their teeth each day, they increase the number of times they go to the gym each week. This is best described as an example of

Accepted Answer

A positive correlation is when two variables move in the same direction, meaning as one variable increases, the other also increases, or as one decreases, the other also decreases. In this case, as the number of times people brush their teeth increases, the number of times they go to the gym also increases, indicating a positive correlation.

Question 15

A research project is conducted by offering a randomly selected 75 of the 200 local dog owners a chance to have their dogs wear a new flea collar for three months to see if the collar reduces the incidence of fleas. 50 of the 75 randomly selected dog owners agree to the offer, and 25 of those drop out of the study before the end of the three months. Using the intention to treat method, the results from how many of the randomly selected dogs should be included in the research project?

Accepted Answer

In the intention to treat method, all participants who were originally allocated to each group are included in the analysis, regardless of whether they completed the study, adhered to the intervention, or dropped out. Therefore, all 75 dogs originally selected should be included in the analysis.

Question 16

Refer to the information provided in Scenario 22.3 below to answer the question(s) that follow.
SCENARIO 22.3: Consider a local high school that has 300 sophomores considered to be at-risk students. A privately-sponsored after-school sports program has been established to try to help at-risk students succeed in finishing high school. The local government wants to know if this program reduces the students' probability of dropping out of high school before the end of their junior year, and decides to randomly sample 150 of the 300 at-risk sophomores and invite them to attend the after-school program at no cost. 100 students accept the invitation, and by the end of their junior year, the drop-out percentage of the 100 students who attended the program was lower than the drop-out percentage of the 200 students who did not attend the program.
-Refer to Scenario 22.3. The efficacy of this program can be best measured by comparing

Accepted Answer

The efficacy of the program is best measured by comparing the outcomes of all students who were offered the program (regardless of whether they attended) to those who were not offered the program. This approach, as described in option C, accounts for the potential self-selection bias of students who choose to attend the program and provides a more accurate measure of the program's impact on the entire group of at-risk students.

Question 17

Refer to the information provided in Scenario 22.3 below to answer the question(s) that follow.
SCENARIO 22.3: Consider a local high school that has 300 sophomores considered to be at-risk students. A privately-sponsored after-school sports program has been established to try to help at-risk students succeed in finishing high school. The local government wants to know if this program reduces the students' probability of dropping out of high school before the end of their junior year, and decides to randomly sample 150 of the 300 at-risk sophomores and invite them to attend the after-school program at no cost. 100 students accept the invitation, and by the end of their junior year, the drop-out percentage of the 100 students who attended the program was lower than the drop-out percentage of the 200 students who did not attend the program.
-Refer to Scenario 22.3. Based on the information in the scenario, the 100 students who accepted the offer to attend the after-school program is an example of

Accepted Answer

The 100 students who accepted the offer to attend the after-school program represent a self-selected group, which can lead to selection bias because they might have characteristics that make them more likely to stay in school compared to those who did not choose to participate.

Question 18

Debbie realizes that her twin brother Dudley breaks out in hives every time he eats oysters, and concludes that when Dudley feels a case of hives coming on, he must get a craving for oysters. Debbie is

Accepted Answer

Debbie's conclusion is likely incorrect because it is more plausible that eating oysters causes Dudley's hives, rather than Dudley craving oysters when he is about to break out in hives.

Question 19

Refer to the information provided in Scenario 22.3 below to answer the question(s) that follow.
SCENARIO 22.3: Consider a local high school that has 300 sophomores considered to be at-risk students. A privately-sponsored after-school sports program has been established to try to help at-risk students succeed in finishing high school. The local government wants to know if this program reduces the students' probability of dropping out of high school before the end of their junior year, and decides to randomly sample 150 of the 300 at-risk sophomores and invite them to attend the after-school program at no cost. 100 students accept the invitation, and by the end of their junior year, the drop-out percentage of the 100 students who attended the program was lower than the drop-out percentage of the 200 students who did not attend the program.
-Refer to Scenario 22.3. To use the intention-to-treat procedure to measure the effect of the after-school program, you would need to compare

Accepted Answer

The intention-to-treat procedure involves analyzing the outcomes based on the initial treatment assignment, regardless of whether the participants followed through with the treatment. Therefore, comparing the drop-out percentage of all 150 students who were offered the program to the 150 who were not offered the program accurately reflects this approach.

Question 20

Zachary notices that every time he washes his car, it rains the next day. He concludes that washing his car causes the next day's rain. Zachary is

Accepted Answer

The answer of Zachary notices that every time he washes...

Quiz 22: Critical Thinking About Research