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Sampling and Experimentation — Test Answers

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1
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Which of the following would benefit this experiment the most?

A
This experiment should be single blind. The subjects do not know which treatment they are receiving to control for the placebo effect, but the technicians need to know which group received which treatment.
B
This experiment should be single blind. The subjects know which treatment they are receiving but the technicians do not know which group received which treatment, so the response being measured is not affected.
C
This experiment should be double blind. Neither the subject nor the technician should know which group is receiving the new medication and which is receiving the placebo. This method would control for the placebo effect and prevent any effect on the response.
D
This experiment should not use blinding. It is unethical for the subjects not to know which treatment they are receiving, placebo or new medication, and for the technicians not to know which group received which treatment.
2
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Race organizers want to survey the participating runners on the quality of the running course. Which of the following uses systematic random sampling?

A
Select the first 15 finishers and the last 15 finishers to take the survey.
B
Select the 5th finisher (with the number 5 being randomly chosen) to survey, then survey every 15th finisher after that.
C
Sort all of the runners’ names alphabetically, then randomly choose 2 letters and survey all participants whose last name begins with one of those letters.
D
Randomly select 15 percent of the male participants and 15 percent of the female participants.
3

A citizen wants to propose to the city council extending the hours at the local public library on some weekdays. To measure support for extended hours, the citizen visits neighborhood homes and asks adults the following: "Would you agree that the closing time of the library should be extended by one hour on weekdays to accommodate working families?” Of the 212 adults surveyed, 86 percent agreed with the statement. Which of the following statements about the results is true?

A
The 86 percent support provides substantial evidence that the library hours should be extended.
B
More families should be asked the same question to be sure of community support.
C
The survey suffers from voluntary response bias and may not estimate true support for the extended hours.
D
The survey suffers from question wording bias and may not represent true support for the extended hours.
4

A teacher has 36 students who are sitting in 6 rows of 6 desks. He wants to survey the students about the homework policy. Which of the following uses cluster sampling?

A
List all of the students alphabetically. Survey the 2nd person (with the number 2 being randomly chosen), then survey every 5th student after that.
B
Randomly assign the students to desks. Number the rows 1 to 6. Use a random number table to select a number from 1 to 6, then survey every student in that row.
C
Randomly assign the students to desks, and number the students 01–36. Use a random number table to generate a sample of students.
D
List all of the students alphabetically. Survey 1 randomly chosen student whose last name begins with A , then continue the process through the alphabet.
5

The CEO of a company wants to determine if taking the employees to a company retreat would boost their morale. He decides to use a random number table to survey a simple random sample of 50 of the 250 employees. Which of the following correctly labels the population of employees?

A
0–250
B
1–250
C
000–250
D
001–250
6

A greenhouse owner wants to test the effectiveness of a new fertilizer on African violets. She has 60 violet seedlings that were grown for 8 weeks. She wants to test the new fertilizer on 10 of the plants, and decides to use a simple random sample to select them. Which of the following statements is true?

A
She needs to put the plants in 6 groups of 10 and randomly select 1 of the groups.
B
She needs to select the 10 biggest plants to test the new fertilizer.
C
She needs to number each plant 1–60 and randomly select 10 plants.
D
She needs to select the 10 smallest plants to test the new fertilizer.
7

Several members of a running club would like to survey the rest of the members to determine which 5K races the club should enter. They decide to use a random number table to sample 10 of the 78 members. The members are assigned the numbers 01–78. Refer to the given line from a random number table. Which numbers represent the first 5 members selected? 24000 75983 62200 91518 11198 88936

A
24, 75, 36, 22, 51
B
24, 00, 07, 59, 83
C
24, 75, 98, 36, 22
D
24, 07, 59, 62, 20
8

Education researchers are interested in the workload expectations of freshmen at a local university. Which of the following techniques would give a stratified random sample?

A
Randomly select 10 freshmen from the cafeteria on each of the 5 days of the first school week.
B
Randomly select 10 freshmen from each of the majors at the university.
C
Randomly select 1 professor at the university and have them survey all of their freshman students.
D
Survey the students in some randomly selected freshman seminar classes, since freshmen are randomly put into those classes.
9

A city official would like to know if there is public support for increasing funding for arts programs. To collect data, the city official stands outside a concert hall after a show and surveys every 25th person to exit and asks their opinion about raising funds for the arts. Which of the following describes the population in this scenario?

A
all city residents who support the arts
B
all residents of the city
C
the people surveyed by the city official
D
the members of the city council
10

City planners plan to survey residents to estimate the proportion of city residents who use public transportation at least once a week. Which of the following methods describes a voluntary response survey?

A
City planners stand outside an office building and survey workers.
B
City planners take a random sample of local homes and survey the residents.
C
City planners hand out surveys to parents at a youth soccer game.
D
City planners email a survey to all residents in the community.
11

An automotive service center would like feedback on its customer service. Each customer receives a printed card after they pay for services with a short survey on which customer service is ranked on a scale from 1 (least satisfied) to 5 (most satisfied). Customers can then choose to submit the card in a box on their way out of the store. The store manager finds that 140 cards were filled out in the past week, with an average customer satisfaction score of 2 point 4 7 Which type of bias is most likely to be present in the survey results?

A
This is undercoverage bias because some types of customers may not have received cards.
B
This is nonresponse bias because many customers may choose to not fill out the cards.
C
This is response bias because customers may not be truthful about their experience with customer service.
D
This is question wording bias because the customer service score levels may not be clear to customers.
12

Does this procedure describe a completely randomized design for this experiment?

A
Yes, the treatments were randomly assigned to the dogs.
B
No, the names were taken in order, so there was no randomization.
C
No, the veterinarian did not use dogs of the same breed.
D
Yes, the treatment groups have the same number of dogs.
13

Which method describes an experiment?

A
Both methods describe experiments because both fonts are used on the assignment.
B
Method B is an experiment because the students are randomly assigned a font.
C
Method A is an experiment because the students choose their own font.
D
Neither method describes an experiment because a third font should be included for comparison.
14

Using the dotplot and the difference in mean distances from the samples, is there convincing evidence that the new golf ball travels farther than the original golf ball?

A
No, because a difference in mean distances of 2 point 6 feet or less occurred 166 out of 200 times, meaning the difference is not statistically significant. There is not convincing evidence the new golf ball travels farther than the original golf ball.
B
No, because a difference in mean distances of 2 point 6 feet or more occurred 34 out of 200 times, meaning the difference is not statistically significant. There is not convincing evidence the new golf ball travels farther than the original golf ball.
C
Yes, because a difference in mean distances of 2 point 6 feet or more occurred only 34 out of 200 times, meaning the difference is statistically significant. There is convincing evidence the new golf ball travels farther than the original golf ball.
D
Yes, because a difference in mean distances of 2 point 6 feet or less occurred 166 out of 200 times, meaning the difference is statistically significant. There is convincing evidence the new golf ball travels farther than the original golf ball.
15

Which of the following is the best description of the experimental design?

A
completely randomized design
B
matched pairs design
C
randomized block design
D
observational study
16

Which component is missing from the biologist’s process?

A
The biologist did not randomly assign the individual bats to the treatment groups.
B
The biologist did not use the appropriate number of treatment groups.
C
The biologist did not use proper labeling on the pieces of paper.
D
The biologist did not randomly choose the weather on the night for bat capture.
17

Which method describes an experiment?

A
Both methods are experiments because the additive is used in a new tank of gas in both methods.
B
Method B is an experiment because every car receives the additive.
C
Method A is an experiment because the additive is used with a new tank of gasoline.
D
Method A is an experiment because random assignment determines which cars receive the additive and which cars do not.
18

Which of the following is a valid conclusion?

A
Inferences cannot be made about the population of fabric from which the pieces were cut. The conclusion can be made that detergent A cleans better than detergent B for the fabric from these bolts.
B
Inferences can be made about the population of fabric from which the pieces were cut. The conclusion cannot be made that detergent A cleans better than detergent B for the fabric from these bolts.
C
Inferences can be made about the population of fabric from which the pieces were cut. The conclusion can be made that detergent A cleans better than detergent B for the fabric from these bolts.
D
Inferences cannot be made about the population of fabric from which the pieces were chosen. The conclusion cannot be made that detergent A cleans better than detergent B for the fabric from these bolts.
19

Which of the following statements is true about the benefits of random assignment?

A
The variability between each subject would be evenly distributed between the two groups, so any observed differences in the level of irritation between the two groups are more likely due to the new cream.
B
The variability between each subject may not be evenly distributed between the two groups, so any observed differences in the level of irritation between the two groups may or may not be due to the new cream.
C
The variability between each subject may not be evenly distributed between the two groups, so any observed differences in the level of irritation between the two groups would not be due to the new cream.
D
The variability between each type of cream would be evenly distributed between the two groups, so any observed differences in the level of irritation between the two groups are guaranteed to be due to the subjects.
20

Using this dotplot and the difference in proportions from the samples, is there convincing evidence that the new additive was more effective?

A
No, because a difference in proportions of 0 point 4 or less occurred 193 out of 200 times, meaning the difference is not statistically significant and the new additive is not more effective.
B
No, because a difference in proportions of 0 point 4 or more occurred 7 out of times, meaning the difference is not statistically significant and the new additive is not more effective.
C
Yes, because a difference in proportions of 0 point 4 or more occurred 7 out of 200 times, meaning the difference is statistically significant and the new additive is more effective.
D
Yes, because a difference in proportions of 0 point 4 or less occurred 193 out of 200 times, meaning the difference is statistically significant and the new additive is more effective.

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