Deck 12: Experimental Design: Controlling Variation

Question 1

A chocolate chip manufacturer has developed a new recipe for its chocolate chips and is planning a consumer taste test. Researchers in the test kitchen want to measure whether there is a difference in consumer opinions between the old recipe and the new recipe. Company researchers believe that consumer reaction to the new chip will depend on age so they decide to block on age. To do this, they create blocks for consumers between the ages 12- 18 years, 19- 25 years, 26- 32 years, and 32 years and older. They then randomly assign subjects in each block to taste cookies made with the new and old recipe chocolate chip. Following the taste test, participants respond to a questionnaire about the cookies they tasted. Is this an effective design for this study?

A)No
B)Yes

Answer 1

Yes

Question 2

Use the following information to answer the question. A researcher wonders whether speed of service at a diner is affected by whether a male customer is wearing a suit jacket. The researcher used the following study design to collect data: The researcher chose five diners in a large city and recorded the number of male customers that wore a suit jacket during a two week period. He also records how long it took a waiter or waitress to address the customer. He finds that male customers who wear suit jackets were addressed by the wait staff faster than male customers who did not wear a suit jacket.
Choose the statement that correctly explains why we can or cannot make a cause- and- effect conclusion.

A)This was an experimental study so we conclude that wearing a suit jacket caused a male customer to be addressed faster.
B)Since this was a controlled observational study we can conclude that there was a cause- and- effect relationship.
C)This was an observational study. Since random assignment was not used, we cannot conclude that getting addressed faster was caused by wearing a suit jacket.
D)The male customers (and diners)were not selected from a larger population, so we cannot conclude that there was a cause- and- effect relationship.

Answer 2

This was an observational study. Since random assignment was not used, we cannot conclude that getting addressed faster was caused by wearing a suit jacket.

Question 3

Suppose a sociologist reports that after analyzing data that he collected on the drinking habits of college students, he decided to test that hypothesis that there is no difference in the drinking habits of fourth year students and first year students. What research error has been committed by the sociologist?

A)Media bias
B)Publication bias
C)Data dredging
D)Clinical significance

Answer 3

Data dredging

Question 4

Which of the following statements is not true about a cluster sampling plan?

A)In cluster sampling, some natural or convenient distinction is used to divide the population.
B)If carefully executed, a cluster sampling plan will produce estimates that are as precise as possible.
C)Cluster sampling can make it easier to access very large populations.
D)All of these statements are true of a cluster sampling plan.

Question 5

The Sirex Noctilio, a wood wasp, is considered an invasive species in Michigan and can harm and even kill pine trees. To detect the presence of the wood wasp on public land, environmental researchers partition land into one acre parcels then randomly select a sample of parcels to be fully inspected for the presence of the wood wasps in pine trees. What kind of sampling does this illustrate?

A)Stratified
B)Random Sampling
C)Systematic
D)Cluster

Question 6

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Gaining weight after giving birth for the first time leads to pregnancy- related diabetes during second pregnancy, a new study finds.
Headline B: Women who gain weight after giving birth for the first time dramatically increase their risk of developing pregnancy- related diabetes during their second pregnancy, a new study suggests.
Was the study referenced most likely a controlled experiment or an observational study?

A)Controlled experiment
B)Observational study

Question 7

Which of the following is not a benefit of a stratified sampling plan?

A)Statistics from a stratum will reflect the parameters of the population as a whole.
B)Increased precision
C)Members of a stratum, or similar group, are likely to respond the same, which leads to results with lower variability.
D)All of these are benefits of a stratified sampling plan.

Question 8

Which of the following statements is not true about a systematic sampling plan?

A)Systematic sampling works best when objects are received in sequence during a specific time period and the characteristic of interest can be reasonably assumed to be randomly mixed during the time period in which the data will be collected.
B)A systematic sampling plan is often used for exit polls and quality control studies.
C)With systematic sampling, objects from the population are sampled at regular intervals.
D)All of these statements are true for a systematic sampling plan.

Question 9

A newspaper reporter is interested in the outcome of a local election on a controversial issue. She knows that opinions of voters who visit the polls in the morning could be different than those who visit later in the day and she does not want a biased sample. Which sampling method is likely to result in an unbiased sample?

A)A systematic sample of every tenth voter throughout the day.
B)A cluster sample of all the voters who visit the polls between 8:00 am and 9:00 am and between 5:00 pm and 6:00 pm.
C)A large sample of voters that have been stratified by age.
D)None of these.

Question 10

Suppose a new engine additive is designed to improve performance in race cars and researchers wish to test the effectiveness of the new additive. On a closed race course, the individual race times for forty race cars are recorded. The race times (on the same course)for each of the cars after being treated with the engine additive are then recorded. Which test design would be most appropriate for this scenario?

A)Paired t- test
B)Two- sample t- test
C)None of these

Question 11

Which of the following is not an important principle that should always be kept in mind when reading research articles containing statistical research results?

A)Stick to peer- reviewed journals.
B)Be wary of conclusions based on very complex statistical or mathematical models.
C)Don't rely solely on the conclusions of any single paper
D)All of these are important principles.

Question 12

Which of the following statements is not true about a cluster sampling plan?

A)In cluster sampling, the clusters contain objects that are as similar as possible.
B)If carefully executed, a cluster sampling plan will produce estimates that are as precise as possible.
C)Cluster sampling can make it easier to access very large populations.
D)All of these statements are true of a cluster sampling plan.

Question 13

Use the following information to answer the question. Which treatment is most effective at treating carpet stains: vinegar, ammonia, or hydrogen peroxide? In a study, researchers randomly assigned 55 carpet samples with identical stains to one of three groups. Depending on which group they were assigned to, each carpet sample received a home remedy of water mixed with vinegar, ammonia, or hydrogen peroxide. Afterwards, each carpet sample was examined and any remaining stain was measured. Researchers found that a vinegar and water mixture produced better results than both ammonia and hydrogen peroxide.
Choose the statement that restates the conclusion of the study in terms of cause- and- effect conclusion.

A)A water and ammonia mixture effectively treats carpet stains compared to ammonia and hydrogen peroxide.
B)People who use water and vinegar to treat carpet stains will have fewer visible carpet stains.
C)A water and vinegar mixture effectively treats carpet stains compared to ammonia and hydrogen peroxide.

Question 14

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Married men who gain weight following the birth of their first child dramatically increase their risk of further weight gain following the birth of more children, a new study suggests.
Headline B: Married male weight gain after the birth of the first child leads to additional weight gain following the birth of more children, a new study finds.
Which one has language that suggests a cause- and- effect relationship?

A)Headline A
B)Headline B

Question 15

Purple Loosetrife is considered an invasive plant in Michigan. To detect the presence of Purple Loosetrife on public land, environmental researcher's partition land into one acre parcels then randomly select a sample of parcels to be fully inspected for the presence of Purple Loostrife. What kind of sampling does this illustrate?

A)Cluster
B)Systematic
C)Stratified
D)Random Sampling

Question 16

Use the following information to answer the question. Which treatment is most effective at treating carpet stains: vinegar, ammonia, or hydrogen peroxide? In a study, researchers randomly assigned 55 carpet samples with identical stains to one of three groups. Depending on which group they were assigned to, each carpet sample received a home remedy of water mixed with vinegar, ammonia, or hydrogen peroxide. Afterwards, each carpet sample was examined and any remaining stain was measured. Researchers found that a vinegar and water mixture produced better results than both ammonia and hydrogen peroxide.
Was this a controlled experiment or an observational study?

A)Observational Study
B)Controlled Experiment

Question 17

Use the following information to answer the question. Which treatment is most effective at treating head lice: Benzyl alcohol lotion, dandruff shampoo, or mayonnaise? In a study, researchers randomly assigned 55 subjects with head lice to one of three groups. All subjects had similar cases of head lice. Depending on which group they were assigned to, subjects received an over- the- counter remedy of Benzyl alcohol lotion, dandruff shampoo, or mayonnaise, which was applied by a trained professional. Afterwards, each subject was examined and any lice or eggs found were counted. Researchers found that Benzyl alcohol lotion produced better results than both dandruff shampoo and mayonnaise.
Choose the statement that restates the conclusion of the study in terms of cause- and- effect conclusion.

A)Mayonnaise effectively treats head lice.
B)Benzyl alcohol lotion effectively treats head lice compared to mayonnaise and shampoo.
C)People who use Benzyl alcohol lotion have lower instances of head lice than those who used shampoo or mayonnaise.

Question 18

Suppose a gumball manufacturer decides to inspect every twenty- fifth gumball for defects. What kind of sampling does this illustrate?

A)Cluster
B)Systematic
C)Stratified
D)Random Sampling

Question 19

Suppose a large endowment has been left to your city by a private donor. The city council has decided that the endowment should be used to build an activity center near the center of town. One option is to build an activity center for senior citizens. It is decided that a stratified sampling plan would be the best way to get input from the public since opinions within a strata are likely to be similar. Which method for stratifying seems to be most reasonable for this scenario?

A)Stratify by age.
B)Stratify by income.
C)Stratify by gender.
D)None of these.

Question 20

Suppose a manufacturer of rearview mirrors decides to inspect every fifteenth part for defects. What kind of sampling does this illustrate?

A)Systematic
B)Stratified
C)Random Sampling
D)Cluster

Question 21

Which of the following statements is not true about a systematic sampling plan?

A)A systematic sampling divides the population into mini- populations that will have lower variability.
B)Systematic sampling works best when objects are received in sequence during a specific time period and the characteristic of interest can be reasonably assumed to be randomly mixed during the time period in which the data will be collected.
C)With systematic sampling, objects from the population are sampled at regular intervals.
D)All of these statements are true for a systematic sampling plan.

Question 22

Suppose it was reported on the news that a recent study concluded that the probability that you will get brain cancer if you use a cell phone more than doubled from 1 in 460,000 to 1 in 230,000. Choose the statement that best summarizes the significance of this result.

A)Although this result may have statistical significance, it does not have clinical significance since the probability that you will get brain cancer if you use cell phone is still so small that it is unlikely to have a meaningful affect on lives.
B)Many would say that this result does not have clinical or statistical significance because the probabilities are so small that they are meaningless.
C)Although this result may have clinical significance, it does not have statistical significance since the probability that you will get brain cancer if you use cell phone is still so small that it is unlikely to have a meaningful affect on lives.
D)Many would say that this result has both clinical and statistical significance because the probability more than doubled and this result could have a significant impact on lives.

Question 23

Suppose a sociologist is interested in finding out if there is an association between gender and opinions on human cloning. Which test design would be most appropriate for this scenario?

A)Paired t- test
B)Two- sample t- test
C)Chi- square
D)ANOVA

Question 24

An office building janitorial company is interested in the opinions of people who visit the office building on a typical day. He thinks that opinions of people who visit the office building in the morning could be different than those who visit later in the day and he does not want a biased sample. Which sampling method is likely to result in an unbiased sample?

A)A large sample of people who visit the building that have been stratified by age.
B)A cluster sample of all the people who visit the office building between 8:00 am and 9:00 am and between 5:00 pm and 6:00 pm.
C)A systematic sample of every tenth person who visits the office building throughout the day.
D)None of these.

Question 25

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Gaining weight after giving birth for the first time leads to pregnancy- related diabetes during second pregnancy, a new study finds.
Headline B: Women who gain weight after giving birth for the first time dramatically increase their risk of developing pregnancy- related diabetes during their second pregnancy, a new study suggests.
Which one has language that suggests a cause- and- effect relationship?

A)Headline B
B)Headline A

Question 26

Which energy drink is better? In a study, researchers randomly assigned 50 similar adults to one of three groups. All subjects were allowed to sleep for eight hours followed by staying awake for ten hours. Depending on which group they were assigned to, subjects then drank 12 ounces of strong coffee, a name brand "5- hour" energy drink, or 16 oz of a name brand sports drink containing caffeine and vitamins. Afterwards, subjects were measured for mental fatigue. Researchers found that the adults that drank strong coffee after being awake for ten hours were less fatigued than either those who drank the "5- hour" energy drink or the sports drink. For this controlled experiment, identify the treatment and the response variables.

A) Treatment: Strong coffee, 5-hour energy drink, and sports drink. Response: Change in mental
fatigue.
B) Treatment: Strong coffee only. Response: Change in mental fatigue.
C) Treatment: Change in mental fatigue. Response: Strong coffee, 5-hour energy drink, and
sports drink

Question 27

Suppose it was reported on the news that a recent study concluded that the probability that you will get brain cancer if you use a cell phone more than doubled from 1 in 460,000 to 1 in 230,000. Choose the statement that best summarizes the significance of this result.

A)Many would say that this result does not have clinical or statistical significance because the probabilities are so small that they are meaningless.
B)Many would say that this result has both clinical and statistical significance because the probability more than doubled and this result could have a significant impact on lives.
C)Although this result may have clinical significance, it does not have statistical significance since the probability that you will get brain cancer if you use cell phone is still so small that it is unlikely to have a meaningful affect on lives.
D)Although this result may have statistical significance, it does not have clinical significance since the probability that you will get brain cancer if you use cell phone is still so small that it is unlikely to have a meaningful affect on lives.

Question 28

Use the following information to answer the question. A researcher wonders whether speed of service at a diner is affected by whether a male customer is wearing a suit jacket. The researcher used the following study design to collect data: The researcher chose five diners in a large city and recorded the number of male customers that wore a suit jacket during a two week period. He also records how long it took a waiter or waitress to address the customer. He finds that male customers who wear suit jackets were addressed by the wait staff faster than male customers who did not wear a suit jacket.
Choose the statement that correctly explains why we can or cannot generalize these results to a larger population.

A)The male customers were randomly selected to participate in the study so the results can be generalized to the larger population.
B)The male customers were not randomly assigned to wear a suit jacket so the results cannot be generalized to beyond the sample.
C)This was an observational study so results can be generalized to a larger population.
D)The male customers (and diners)were not selected from a larger population, so the results cannot be generalized beyond the sample.

Question 29

Use the following information to answer the question. Which treatment is most effective at treating head lice: Benzyl alcohol lotion, dandruff shampoo, or mayonnaise? In a study, researchers randomly assigned 55 subjects with head lice to one of three groups. All subjects had similar cases of head lice. Depending on which group they were assigned to, subjects received an over- the- counter remedy of Benzyl alcohol lotion, dandruff shampoo, or mayonnaise, which was applied by a trained professional. Afterwards, each subject was examined and any lice or eggs found were counted. Researchers found that Benzyl alcohol lotion produced better results than both dandruff shampoo and mayonnaise.
Was this an observational study or a controlled experiment?

A)Observational Study
B)Controlled Experiment

Question 30

Suppose state lawmakers are interested in finding out whether a newly instituted state program about distracted driving is effective. A statistician divides the state into three regions then randomly selects a sample of adult licensed drivers from each region. Participants are then asked to fill out a questionnaire about distracted driving. What kind of sampling does this illustrate?

A)Stratified
B)Random Sampling
C)Cluster
D)Systematic

Question 31

Suppose a large endowment has been left to your city by a private donor. The city council has decided that the endowment should be used to build a recreation park near the center of town. One option is to build a skate park. It is decided that a stratified sampling plan would be the best way to get input from the public since opinions within a strata are likely to be similar. Which method for stratifying seems to be most reasonable for this scenario?

A)Stratify by gender.
B)Stratify by income.
C)Stratify by age.
D)None of these.

Question 32

Suppose state lawmakers are interested in finding out whether a newly instituted elementary school program about bullying is effective. A statistician divides the state into three regions then randomly selects a sample of thirty elementary schools from each region. Students at the selected schools complete a questionnaire about bullying. What kind of sampling does this illustrate?

A)Random Sampling
B)Cluster
C)Systematic
D)Stratified

Question 33

A ranch salad dressing manufacturer has developed a new recipe for its ranch dressing and is planning a consumer taste test. Researchers in the test kitchen want to measure whether there is a difference in consumer opinions between the old recipe and the new recipe. Company researchers believe that consumer reaction to the new dressing will depend on gender so they decide to block on gender. To do this, they create blocks for female adult consumers and male adult consumers. They then randomly assign subjects in each block to taste dressings using the new and old recipe. Following the taste test, participants respond to a questionnaire about the dressings they tasted. Is this an effective design for this study?

A)Yes
B)No

Question 34

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Married men who gain weight following the birth of their first child dramatically increase their risk of further weight gain following the birth of more children, a new study suggests.
Headline B: Married male weight gain after the birth of the first child leads to additional weight gain following the birth of more children, a new study finds.
Was the study referenced most likely a controlled experiment or an observational study?

A)Controlled experiment
B)Observational study

Question 35

Use the following information to answer the question. A researcher wonders whether receiving a job offer is effected by whether an interviewee wears a red tie. The researcher used the following study design to collect data: The researcher chose five large companies in a large city and observed the tie color of all interviewees during a two week period. He also records whether the person was hired by the company. He finds that interviewees who wear red ties are more likely to be hired than interviewees who do not wear red ties.
Choose the statement that correctly explains why we can or cannot make a cause- and- effect conclusion.

A)This was an observational study. Since random assignment was not used, we cannot conclude that getting hired was caused by wearing a red tie.
B)Since this was a controlled observational study we can conclude that there was a cause- and- effect relationship.
C)The interviewees (and companies where they were interviewed)were not selected from a larger population, so we cannot conclude that there was a cause- and- effect relationship.
D)This was an experimental study so we conclude that wearing a red tie caused an interviewee to be hired.

Question 36

Which of the following is not a primary factor that affects the power of a test?

A)Sample size
B)Natural variability within the population
C)The sample standard deviation
D)The size of the true difference between treatment groups

Question 37

Use the following information to answer the question. A researcher wonders whether receiving a job offer is effected by whether an interviewee wears a red tie. The researcher used the following study design to collect data: The researcher chose five large companies in a large city and observed the tie color of all interviewees during a two week period. He also records whether the person was hired by the company. He finds that interviewees who wear red ties are more likely to be hired than interviewees who do not wear red ties.
Choose the statement that correctly explains why we can or cannot generalize these results to a larger population.

A)The interviewees were not randomly assigned to wear a red tie to the interview so the results cannot be generalized to beyond the sample.
B)The interviewees (and companies where they interviewed)were not selected from a larger population, so the results cannot be generalized beyond the sample.
C)The interviewees were randomly selected to participate in the study so the results can be generalized to the larger population.
D)This was an observational study so results can be generalized to a larger population.

Question 38

Which workout recovery drink is better: water, a fortified sports drink, or chocolate milk? In a study, researchers randomly assigned 50 similar athletes to one of three groups. All subjects participated in the same workout. Depending on which group they were assigned to, subjects then drank 12 ounces of water, a fortified sports drink, or chocolate milk. Afterwards, subjects were measured for muscle fatigue. Researchers found that the athletes that drank chocolate milk after a workout recovered from muscle fatigue faster than either those who drank water or the sports drink. For this controlled experiment, identify the treatment and the response variables.

A) Treatment: Strong coffee, 5-hour energy drink, and sports drink. Response: Change in mental
fatigue.
B) Treatment: Strong coffee only. Response: Change in mental fatigue.
C) Treatment: Change in mental fatigue. Response: Strong coffee, 5-hour energy drink, and
sports drink.

Question 39

Which of the following is not a primary factor that affects the power of a test?

A)The size of the true difference between treatment groups
B)Sample size
C)The sample standard deviation
D)Natural variability within the population

Question 40

Which of the following is not a benefit of a stratified sampling plan?

A)Members of a stratum, or similar group, are likely to respond the same, which leads to results with lower variability.
B)Increased precision
C)Statistics from a stratum will reflect the parameters of the population (from which the stratum was drawn)as a whole.
D)All of these are benefits of a stratified sampling plan.

Question 41

Use the following information to answer the question. A researcher wonders whether length of time that it takes to hail a taxi is affected by the gender of the person hailing the taxi. The researcher used the following study design to collect data: The researcher chose five busy intersections in a large city and recorded the number of males and females who hailed a taxi. He also records how long it took to get a taxi to stop. He finds that male customers waited a shorter period of time than females waited for a taxi.
Explain why we can or cannot generalize these results to a larger population.

Question 42

Write at least two questions that you should ask yourself when reading articles containing statistical research results. Explain why these questions are important.

Question 43

Suppose the CEO of a large corporation is interested in finding out whether a newly instituted program about professionalism in the workplace is effective. A statistician divides the employees into three job types then randomly selects a sample of employees from each job type. Participants are then asked to fill out a questionnaire about professionalism in the workplace. What kind of sampling does this illustrate?

Question 44

Use the following information to answer the question. A researcher wonders whether length of time that it takes to hail a taxi is affected by the gender of the person hailing the taxi. The researcher used the following study design to collect data: The researcher chose five busy intersections in a large city and recorded the number of males and females who hailed a taxi. He also records how long it took to get a taxi to stop. He finds that male customers waited a shorter period of time than females waited for a taxi.
Restate the conclusion of the study in terms of a cause- and- effect conclusion. Explain why we can or cannot make a cause- and- effect conclusion.

Question 45

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Children who view advertisements for fast food dramatically increase their risk of becoming obese adolescents, a new study suggests.
Headline B: Viewing advertisements for fast food leads to childhood obesity, a new study finds.
Was the study referenced most likely a controlled experiment or an observational study? Explain.

Question 46

Describe a situation where a systematic sampling plan would be appropriate.

Question 47

A publisher is considering publishing a new magazine about environmentally- friendly living in the city and plans to gage interest in the magazine using potential consumers. Company researchers want to measure whether there is a difference in opinion between the new magazine and the competing publication. Company researchers believe that consumer reaction to the new magazine will depend on age so they decide to block on age. To do this, they create blocks for consumers between the ages 18- 24 years, 25- 32 years,
33- 45 years, and 46 years and older. They then randomly select two of the blocks to read the first issue of the new magazine and the other two blocks to read a similar competing publication. Following the test, participants respond to a questionnaire about the magazine they read. Is this an effective design for the study? If not, describe an improvement.

Question 48

List three factors that affect the statistical power of a test. Be sure to list the factor over which researchers actually have some control.

Question 49

Suppose it was reported on the news that a recent study concluded that pollutants in the air have dramatically increased our chances of getting a rare form of skin cancer from 1 in 250,000 to 1 in 150,000. Compare the clinical and statistical significance of this result.

Question 50

Use the following information to answer the question. These two headlines are on the same topic.
Headline A: Children who view advertisements for fast food dramatically increase their risk of becoming obese adolescents, a new study suggests.
Headline B: Viewing advertisements for fast food leads to childhood obesity, a new study finds.
Which one has language that suggests a cause- and- effect relationship? Is this problematic? Can you think of a confounding factor other than exposure to fast food advertisements that might cause childhood obesity?

Question 51

Suppose a sleep expert conducts a study to detect the effects of a new
doctor- recommended breathing and relaxation routine on insomnia. Hours of sleep per night were measured for participants before starting the routine and four weeks after using the breathing and relaxation routine just before bed. Which test design would be most appropriate for this scenario? Explain.

Question 52

Use the following information to answer the question. Which treatment is most effective at treating bathroom mildew: water mixed with vinegar, ammonia, or soap? In a study, researchers randomly assigned 55 similar tile samples with similar amounts of mildew to one of three groups. Depending on which group they were assigned to, each tile sample received a home remedy of water mixed with vinegar, ammonia, or soap. Afterwards, each tile sample was examined and any remaining mildew was measured. Researchers found that a soap and water mixture produced better results than both vinegar and ammonia.
Write a statement that restates the conclusion of the study in terms of a cause- and- effect conclusion.

Question 53

Use the following information to answer the question. Which treatment is most effective at treating bathroom mildew: water mixed with vinegar, ammonia, or soap? In a study, researchers randomly assigned 55 similar tile samples with similar amounts of mildew to one of three groups. Depending on which group they were assigned to, each tile sample received a home remedy of water mixed with vinegar, ammonia, or soap. Afterwards, each tile sample was examined and any remaining mildew was measured. Researchers found that a soap and water mixture produced better results than both vinegar and ammonia.
Is this a controlled experiment or an observational study? Explain.

Question 54

Describe one benefit to a cluster sampling plan.

Question 55

Suppose a snow blower manufacturer decides to inspect every seventh snow blower for paint defects. What kind of sampling does this illustrate?

Question 56

Describe one benefit to a stratified sampling plan.

Question 57

Does listening to music improve efficiency for mundane tasks? In a study, researchers randomly assigned 50 similar adults to one of three groups. All subjects were asked to stuff 400 envelopes. Depending on which group they were assigned to, subjects heard Top 40 music, classical music, or no music while they worked. Researchers recorded how long it took the participants to stuff the envelopes. Researchers found that the adults that listened to no music completed the work faster than both the group that listened to Top 40 music and classical music. For this controlled experiment, state the treatment and the response variables.

Question 58

A bank manager is interested in the opinions of people who visit the bank on a typical day. The manager thinks that opinions of people who visit the bank in the morning could be different than those who visit later in the day and he does not want a biased sample. Describe a sampling method that is likely to result in an unbiased sample. Explain.

Question 59

Suppose a large donation has been left to a local community college by a private donor. School officials have decided that one option for the money would be to build a new gymnasium for student and community use. It is decided that a stratified sampling plan would be the best way to get input from the public about this option since opinions within a stratum are likely to be similar. What would be a reasonable way to stratify the population?

Question 60

Asphodelus fistulosus, a noxious weed commonly known as onionweed, is considered an invasive species in New Mexico and can choke out other vegetation. To detect the presence of onionweed on public land, environmental researchers partition land into one acre parcels then randomly select a sample of parcels to be fully inspected for the presence of onionweed. What kind of sampling does this illustrate?