Answers DRHS GA-Statistical ReasoningHow to Experiment Well

How to Experiment Well — Unit test Answers

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A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers placed an ad online asking for volunteers to participate in the study. One hundred subjects replied and were informed that one group would receive the new cream and the other group would receive a cream with no active ingredient. All 100 subjects were exposed to poison ivy. Fifty were then randomly assigned to the group with the new cream, and 50 were randomly assigned to the group with the cream with no active ingredient. After three days, the subjects’ level of irritation was measured.

The overall level of irritation can be compared to see if the new cream had a significant effect.

The level of irritation for both groups can be compared to see if the new cream had a significant effect.

The level of irritation in the treatment group only can be compared to see if the new cream had a significant effect

Since one group received a cream with no active ingredient, the researchers will not be able to determine of the new cream is effective.

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An article in a psychology journal claims that young students who play a musical instrument tend to have higher test scores on state math exams. To assess the claim, a government official considers two methods to collect data.Method 1: Contact many city schools and ask them to provide summary data on state math exam performance and students who participate in music lessons.Method 2: Choose two city schools and provide free music lessons to students who register. At the end of the year, compare state math exam scores for students who participated in the music lessons with the scores for those who did not.

Method 1 is an observational study because past data are collected and analyzed.

Method 2 is an observational study because two city schools are chosen to participate.

Method 2 is an observational study because students can choose to participate in the music lessons.

Both methods are observational studies because both include students who do and do not play a musical instrument.

Which of the following is not true about cluster sampling?

Cluster sampling has the advantage of reducing sampling variability.

Cluster sampling has the advantage of saving time and money.

Cluster sampling uses clusters, which are miniature, nonoverlapping versions of the population.

Cluster sampling uses randomly selected clusters and samples everyone within each cluster.

A biology student wants to determine if using a fertilizer would help promote growth of new babies in spider plants. The student chooses 100 baby spider plants to be used in the study. 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. Fifty of the plants will be given the fertilizer treatment and the other 50 plants will not receive any fertilizer. After one year, the shoots will be counted for each plant.

For each plant, flip a coin. If the coin lands on heads, the plant will receive the fertilizer. If the coin lands on tails, the plant will not receive the fertilizer. Continue until 50 plants have been assigned to each of the two treatment groups.

Group the plants based on size with the 50 biggest plants in one group and the 50 smallest plants in the other group. Flip a coin, and if it lands on heads, give the first group of 50 the fertilizer. If it lands on tails, give the second group of 50 the fertilizer.

Number the plants 00–99 and, using a random number table, read the digits two at time. Select the first 50 digits. These will represent the plants placed in the fertilizer group. The remaining 50 plants will be placed in the group that does not receive fertilizer.

Number the plants 1–100 and put these numbers into a random number generator. The first 50 unique numbers generated will represent the plants placed in the fertilizer group. The remaining 50 plants will be placed in the group that does not receive fertilizer.

Many movie theaters show advertisements before feature films to increase concession sales. However, many customers complain about the length the advertisements add to their time at the theater. To understand the effect of advertising, a movie theater manager chooses random days during the month when the concession advertisements are not shown. On the remaining days, the concession advertisements are shown as usual. The manager then records the concession sales for each day.

the movie theater patrons

the concession advertisements

the daily theater attendance

the amount of money collected at the concession stand

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 takes the balls to the driving range and hits the 40 new-style golf balls first and then the 40 original-style golf balls. The distance each ball travels is recorded. At the end of the session, the mean distance traveled for the new type of golf ball was found to be significantly greater than the mean distance for the original-style golf ball.

Inferences can be made about all the golf balls produced on that day, and the conclusion can be made that new-style golf balls travel farther than the original-style of golf ball for this golf pro.

Inferences can be made about all the golf balls produced on that day; however, a conclusion cannot be made that new-style golf balls travel farther than the original type of golf ball for this golf pro.

Inferences cannot be made about all the golf balls produced on that day, and a conclusion cannot be made that new-style golf balls travel farther than the original type of golf ball for this golf pro.

Inferences cannot be made about all the golf balls produced on that day; however, the conclusion can be made that new-style golf balls travel farther than the original type of golf ball for this golf pro.

A therapist wants to study the effects of yoga and meditation on stress relief. She has 60 volunteers who experience varying levels of stress. Half of the participants will be assigned to practice yoga for one month and the other half will practice meditation. Before the experiment begins, all of the participants will be asked to rate their stress levels on a scale from 0 to 10, with 0 representing "no stress” and 10 representing "highest level of stress.” At the end of one month, the participants will be asked to rate their stress levels again. The differences in stress levels will be compared.

The volunteers’ names are all placed on equal-sized slips of paper and these slips are put into a hat. The therapist draws 30 slips of paper and the corresponding volunteers are placed into the yoga group. The remaining 30 volunteers are placed in the meditation group. After one month, the stress levels between the two groups are measured and compared.

Volunteers are put together in groups of two based on stress level. For each group of two, a coin is flipped. If it lands on heads, then the first person is placed in the yoga group and if it is tails, then the first person is placed in the meditation group. The other person will be placed in the other group. After one month, the stress levels between the two participants are measured and compared.

The volunteers’ names are all placed on equal-sized slips of paper, and these slips are put into a hat. After the hat is shaken, a slip of paper is drawn and the corresponding volunteer is placed in the yoga group. This is repeated until the yoga group has 30 volunteers. The remaining 30 volunteers are placed in the meditation group. After one month, the stress levels between the two groups are measured and compared.

The volunteers are grouped based on their current stress levels. The 30 volunteers with the highest levels of reported stress are placed in one group and the remaining 30 volunteers are placed in another group. The therapist flips a coin. If it lands on heads, then the group with the highest stress levels will receive the yoga treatment. If it lands on tails, then this group will receive the meditation treatment. After one month, the stress levels will be compared between the two groups.

A doctor wants to determine if a new medication for cholesterol is more effective than the previous medication. The doctor asks her patients if they would like to take part in a study for a new medication, and 30 patients currently taking medication for cholesterol volunteer to participate. Which of the following would be an appropriate procedure for this experiment?

The doctor needs to randomly assign 15 patients to the new medication and 15 to the original medication to even out the variability between the patients.

The doctor needs to assign the first 15 patients to the new medication and 15 to the original medication to even out the variability between patients.

The doctor needs to let the 30 patients choose which medication they are going to take through use of a survey to determine whether they want to participate in the experiment.

The doctor needs to randomly assign the 30 patients to the new medication to even out the variability between the patients and to determine if their cholesterol level is lowered.

A farmer sows 100 seeds of a new type of corn and wants to quickly determine the yield, or total number of ears of corn, for the crop when it has matured. He decides to take a simple random sample of the crop by using a random digit table. What is the fewest number of digits that should be used, given that there are 100 plants in total?

An observational study of suburban towns reveals that towns with more dedicated park land tend to have higher median home prices. A real estate agent suggests that a town’s crime rate is a more accurate predictor of median home price.

the median home price

the crime rate

the distance from a large city

the median home size

What proportion of families own as opposed to rent their home? To find out, an urban planner selected a random sample of 400 families in a large city to participate in a survey about homeownership. Of the 362 families that responded to the survey, 42% reported that they own their home. Which of the following statements about the survey results is true?

A suitable estimate of all families who own their home is 42%.

The survey suffers from voluntary response bias and may not accurately represent the population.

Only 362 responses cannot provide a suitable estimate of families who own their home.

The survey suffers from undercoverage and may not provide a suitable estimate of homeownership.

A trade school would like to measure the long-term success of their graduates after they leave the school. The school emails a survey requesting information from graduates about their work experience. One question asks graduates to share their annual salary, and the results of the question will be shared in a brochure for incoming students. Is it likely that the survey results will provide an accurate estimate of mean annual salary for all of the school’s graduates?

The survey will provide a reasonable estimate of mean annual salary because all graduates were sent the email survey.

The survey will likely overestimate mean annual salary because those with higher salaries may be more likely to respond to the survey.

The survey will likely underestimate mean annual salary because there may be more graduates with lower salaries than higher salaries.

The survey will likely overestimate the mean annual salary because the email was only sent to graduates with jobs in their chosen field.

Which of the following statements is true about systematic random sampling?

Systematic random sampling requires a finite population size.

Systematic random sampling catches all patterns present in the population.

Systematic random sampling can be used, even if knowledge of the entire population is not known.

The starting point can always be the first person seen, as long as the gap between the first and second person is a random number.

A researcher is comparing the effectiveness of three devices designed to help people who snore. There are 60 people who snore participating in the experiment who are labeled 01–60. Using a table of random digits, the researcher will randomly place the participants into three equally sized treatment groups suitable for comparison. Carry out the random assignment using the given selection from a table of random digits, starting with the first row and first column.

00, 29, 90, 75, 71, 17, 37, 76

29, 17, 37, 48, 20, 48, 27, 12

2, 9, 7, 5, 1, 3, 6, 4

29, 17, 37, 48, 20, 27, 12, 23

A tire company wants to determine if tires made with a new type of tread will last longer than tires made with the original type of tread. The company has access to 20 different vehicles and wants to use a randomized block design for the experiment.Which of the following variables would be the best to block the experimental units?

type of vehicle

year of vehicle

make of the vehicle

color of the vehicle

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How to Experiment Well — Unit test Answers

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