AnswersStatistical Modeling - Content Recovery - Part BUnit Test

Unit Test — Unit test Answers

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1
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A biology student wants to determine if using a fertilizer would help promote growth of new babies in spider plants. The student has access to 90 spider plants of three varieties: green, variegated, and curly. They all are potted in the same amount and type of soil, given the same amount of water, and exposed to the same amount of light. After one year, the shoots will be counted for each plant.

A
The plants are numbered 01–90. Using a line from a random number table, the first 45 two-digit numbers, ignoring repeats and the numbers 91–99 and 00, represent the plants that will receive fertilizer. The remaining 45 plants will not receive fertilizer.
B
The plants are paired together based on similar size and numbered 1 and 2. Within each pair, a 6-sided number cube is rolled. If it lands on 1, 2, or 3, plant 1 receives the fertilizer and plant 2 does not receive fertilizer. If the cube lands on 4, 5, or 6, plant 1 does not receive fertilizer and plant 2 receives fertilizer. This is done for each of the 45 pairs of plants.
C
The plants are grouped based on variety. There are 30 plants of each variety. The plants within each variety are numbered 1–30, and the numbers are put in a random number generator. The first 15 unique numbers represent the plants in each variety that will receive fertilizer and the remaining 15 numbers will represent the plants in each variety that will not receive fertilizer.
D
The plants are grouped based on size. The 30 biggest plants are placed in one group and the 30 smallest plants in another other group. The remaining 30 plants are placed in a third group. For each group, a coin is flipped. If the coin lands on heads then the group will receive the fertilizer. If it lands on tails, then the group will not receive fertilizer. Repeat this procedure for the other two groups.
2
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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 hand out surveys to parents at a youth soccer game.
C
City planners take a random sample of local homes and survey the residents.
D
City planners email a survey to all residents in the community.
3

A study is testing the effectiveness of a new allergy medication. Sixty people who reported they have allergies volunteered to be part of the study and were randomly assigned to one of two groups, as shown in the design web.Which of the following accurately describes the benefit of comparison in the experiment shown in the design web?

Question illustration
A
The level of allergic symptoms in both groups can be compared to see if the new medication had a significant effect.
B
The overall level of allergic symptoms can be used to determine if the new allergy medication had a significant effect.
C
The level of allergic symptoms in the group who received the medication can be used to determine if the medication had a significant effect.
D
The level of allergic symptoms in both groups cannot be compared to determine if the medication had a significant effect because one group only received a placebo.
4

A teacher assigns 10 questions for homework and wants to randomly pick 3 questions to be graded. Which of the following procedures would produce a simple random sample?

A
Assign the homework questions the numbers 1–10. Use a random number table to select the first three numbers between 1 and 10. These represent the questions that will be graded.
B
Assign the homework questions the numbers 0 to 9. Use a random number table to select the first three numbers between 0 and 9. These represent the questions that will be graded.
C
Assign the homework questions the numbers 01–10. Use a random number table to select the first three 2-digit numbers between 01 and 10. These represent the questions that will be graded.
D
Assign the homework questions the numbers 0–9. Use a random number table to select the first three unique numbers between 0 and 9. These represent the questions that will be graded.
5

A therapist wants to study the effects of yoga and meditation on stress relief. She has 60 volunteers who experience varying levels of stress. She believes that the volunteers’ professions could have an effect on the results. A preliminary survey reveals that 22 of the volunteers are in high-stress professions. The therapist randomly assigns 11 of these subjects to practice yoga and the remaining 11 to practice meditation. Nineteen of the other 38 volunteers are randomly assigned to practice yoga and the remaining 19 to practice meditation. Before the experiment begins, all the participants will be asked to rate their stress levels on a scale of 0 to 10, with 0 representing "no stress” and 10 representing "highest level of stress.” At the end of one month, the subjects will be asked to rate their stress levels again. The differences in stress levels will be compared for the different stress-relieving activities within the two types of professions.

A
observational study
B
matched pairs design
C
randomized block design
D
completely randomized design
6

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% agreed with the statement. Which of the following statements about the results is true?

A
The 86% 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 question wording bias and may not represent true support for the extended hours.
D
The survey suffers from voluntary response bias and may not estimate true support for the extended hours.
7

A company that manufactures golf balls produces a new type of ball that is supposed to travel significantly farther than the company’s previous golf ball. To determine this, 40 new-style golf balls and 40 original-style golf balls are randomly selected from the company’s production line on a specific day. A golf pro randomly selects a ball, not knowing which type is chosen, and hits it. The difference in mean distances traveled (new – original) for the samples was 2.6 feet. Assuming there is no difference in distance traveled between the two types of golf balls, 200 simulated differences in sample means are displayed in the dotplot.

Question illustration
A
Yes, because a difference in mean distances of 2.6 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.
B
Yes, because a difference in mean distances of 2.6 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.
C
No, because a difference in mean distances of 2.6 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.
D
No, because a difference in mean distances of 2.6 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.
8

An auto-parts store offers a fuel additive that claims to increase a vehicle’s gas mileage. The additive is poured into a vehicle’s gasoline tank after the tank is filled. To measure the claim, two methods to collect data are proposed.Method A: 20 similar police cars owned by a city are selected. After the cars are filled with a fresh tank of gasoline, researchers randomly select 10 of the cars to receive the additive, while the other 10 do not receive the additive. The gas mileage for each car is recorded in miles per gallon.Method B: 20 customers at an auto-parts store receive free coupons for the additive and are asked to use it with their next fresh tank of gasoline. The customers then report their gas mileage with the fuel additive.

A
Method B is an experiment because every car receives the additive.
B
Method A is an experiment because the additive is used with a new tank of gasoline.
C
Both methods are experiments because the additive is used in a new tank of gas in both methods.
D
Method A is an experiment because random assignment determines which cars receive the additive and which cars do not.
9

A study is testing the effectiveness of a new allergy medication. Sixty people who reported they experience allergies were randomly assigned to one of two groups: one with the new medication, and another with a placebo. After two weeks, the subjects were surveyed by technicians to determine their level of allergic symptoms.

A
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.
B
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.
C
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.
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.
10

A consumer agency wants to determine which of two laundry detergents, A or B, cleans better. Fifty 1-square-foot sections of fabric are randomly selected and cut from different bolts of fabric. They are then subjected to the same kinds of stains (grass, mud, coffee). Then 25 pieces are randomly assigned to be cleaned with detergent A, and the remaining 25 pieces are cleaned with detergent B. After being laundered, the pieces of fabric are rated on a scale of 1–10, with 1 being the least clean to 10 being the most clean. The mean rating for detergent A is found to be significantly greater than the mean rating for detergent B.

A
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.
B
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.
C
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.
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.
11

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 select the 10 biggest plants to test the new fertilizer.
B
She needs to select the 10 smallest plants to test the new fertilizer.
C
She needs to number each plant 1–60 and randomly select 10 plants.
D
She needs to put the plants in 6 groups of 10 and randomly select 1 of the groups.
12

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
Randomly select 15% of the male participants and 15% of the female participants.
C
Select the 5th finisher (with the number 5 being randomly chosen) to survey, then survey every 15th finisher after that.
D
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.
13

A community is considering raising funds to pay for improvements to the community swimming pool. To measure the level of interest, community leaders survey patrons of the community pool on a Saturday afternoon. Of the 103 patrons surveyed, 87 approve of raising funds to pay for improvements. Which of the following is a true statement regarding the design and results of the survey?

A
This is a convenience sample and is representative of community support.
B
This is a convenience sample and likely overestimates support for raising funds.
C
This is a voluntary response sample and likely overestimates support for raising funds.
D
This is a voluntary response sample and likely underestimates support for raising funds.
14

A college professor hypothesizes that readers will comprehend more when reading a graphic novel than when reading text with no illustrations. To conduct an experiment, the professor will assign some students to the control group with a reading assignment in paragraph form and other students to the treatment group with a reading assignment in graphic novel form. Afterwards, all the students will take a quiz about the reading to measure comprehension. To assign the groups, the professor will split the students into five groups according to their current grade in the class: A, B, C, D, or F. Within each group, half of the students will be assigned to the treatment group with the graphic novel, and the rest will be assigned to the control group with the paragraph.

A
should be roughly equivalent because the students are from a randomly chosen class.
B
might not be roughly equivalent because the students could have vastly different views about graphic novels.
C
should be roughly equivalent because both groups have a mixture of students with different current grades.
D
might not be roughly equivalent because the students were not labeled and randomly chosen for each group.
15

Research suggests that students could benefit from later school starting times. A school administrative team is considering a proposal to move the starting time of the local schools one hour later than the current start time. To measure interest in the proposal, members of the team randomly select subjects attending a large high school soccer tournament played on the high school grounds on a Saturday morning. The team finds that 58% of those surveyed support a later high school start time. Which type of bias is most likely to be present in the survey results?

A
This is undercoverage bias because adults with older children are more likely to be included in the sample.
B
This is question wording bias because the phrasing of the later start times question may be confusing to some subjects.
C
This is nonresponse bias because some of those selected may choose to not provide their opinion on later start times.
D
This is voluntary response bias because vocal supporters of later start times will be more likely to offer their opinion.
16

A restaurant critic for a newspaper examines the prices restaurants charge for their meals and discovers that the restaurants that raised their prices most over the past year also have the longest wait times for tables.

A
Increasing prices may cause customers to want to visit those restaurants more.
B
Restaurants that do not raise their prices may not see an increase in customers.
C
When customers wait longer for tables, they are more likely to pay higher prices.
D
Higher-quality restaurants might charge more for meals and could also have longer wait times.
17

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 each of the majors at the university.
B
Randomly select 10 freshmen from the cafeteria on each of the 5 days of the first school week.
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.
18

Aeronautical researchers have developed three different processes to pack a parachute. They want to compare the different processes in terms of time to deploy and reliability. There are 1,200 objects that they can drop with a parachute from a plane. Using a table of random digits, the researchers will randomly place the 1,200 items into three equally sized treatment groups suitable for comparison.

A
Randomly number each item with 1, 2, or 3. Assign the items labeled 1 to the process 1 group, assign the items labeled 2 to the process 2 group, and assign the items labeled 3 to the process 3 group.
B
Number each item from 1 to 1,200. Reading from left to right from a table of random digits, identify 800 unique numbers from 1 to 1,200. Assign the items with labels in the first 400 numbers to the process 1 group. Assign the items with labels in the second 400 numbers to the process 2 group. Assign the remaining items to the process 3 group.
C
Number each item from 0000 to 1199. Reading from left to right on a random number table, identify 800 unique four-digit numbers from 0000 to 1199. Assign the items with labels in the first 400 numbers to the process 1 group. Assign the items with labels in the second 400 numbers to the process 2 group. Assign the remaining items to the process 3 group.
D
Select an item, and identify the first digit reading from left to right on a random number table. If the first digit is a 1, 2, or 3, assign the item to the process 1 group. If the first digit is a 4, 5, or 6, assign the item to the process 2 group. If the first digit is a 7, 8, or 9, assign the item to the process 3 group. If the first digit is a 0, skip that digit and move to the next one to assign the item to a group. Repeat this process for each item.
19

A principal wanted to survey students who took a standardized college entry exam about how prepared they felt for the exam. The principal put together a bag of marbles. There was 1 marble for each student, and 20 of the marbles were red. Each student chose a marble, and those who chose the red marbles took the survey. Which sampling method was used?

A
cluster sampling
B
simple random sampling
C
stratified random sampling
D
systematic random sampling
20

A veterinarian knows that the supplement glucosamine is beneficial for dogs’ joints. He wants to determine if a supplement with both glucosamine and chondroitin would be more beneficial than glucosamine alone for dogs’ joint health. The veterinarian asks the owners of dogs with known joint issues if they would be willing to have their dog participate in his study, and 32 owners agree to the study. The dogs’ names are written on equal-sized slips of paper. The veterinarian selects the first 16 slips of paper. These dogs are given the glucosamine treatment.. These dogs are given the glucosamine treatment. The other 16 dogs are given the glucosamine with chondroitin treatment. After six months, the dogs’ joint health is measured for each treatment and compared.

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

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