AnswersStatisticsSampling and Experimentation

Practice Test Answers

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1
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Is this a randomized block design?

A
No, the subjects were not paired by age to determine if it affected the cream’s effectiveness.
B
Yes, the participants are grouped by sun exposure, and then both treatments are randomly assigned within each group.
C
No, the groups have an equal number of subjects.
D
Yes, the subjects could be randomly assigned to two different treatments.
2
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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?

A
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.
B
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.
C
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.
D
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.
3

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. Which of the following correctly labels the population?

A
1–78
B
00–78
C
0–78
D
01–78
4

A community is considering raising funds to pay for improvements to the community swimming pool. To measure the level of interest, community leaders went door-to-door in a few neighborhoods and interviewed residents. Of the 230 residents contacted, 157 support raising funds to pay for improvements. Which of the following represents the sample in this setting?

A
the 230 residents who were interviewed
B
all residents of the community
C
the 157 residents who support raising funds
D
all residents who use the community pool
5

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. What is the confounding variable in this study?

A
the crime rate
B
the median home size
C
the median home price
D
the distance from a large city
6

An urban planner examines police-report data for many cities and towns and discovers that cities with professional football teams tend to have higher numbers of reported small crimes, such as burglary. Which statement best explains the effect of confounding in this relationship?

A
Cities with football teams tend to be large, which means they have more reported small crimes.
B
The football teams are a direct cause of increased small crimes.
C
In cities without football teams, the small crimes often go unreported.
D
Cities without football teams most likely have lower rates of reported small crimes.
7

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 percent reported that they own their home. Which of the following statements about the survey results is true?

A
A suitable estimate of all families who own their home is 42 percent .
B
The survey suffers from undercoverage and may not provide a suitable estimate of homeownership.
C
The survey suffers from voluntary response bias and may not accurately represent the population.
D
Only 362 responses cannot provide a suitable estimate of families who own their home.
8

Which of the following is an advantage of picking samples using stratified random sampling?

A
Stratified random sampling could inadvertently miss patterns in the population.
B
Stratified random sampling reduces sampling variability.
C
Stratified random sampling uses strata, which are easily constructed subgroups of the population.
D
Stratified random sampling does not require a finite population size.
9

A participant in an experiment who incorrectly believes she is receiving treatment and reports an improvement in their condition is experiencing

A
a placebo.
B
the control group.
C
blinding.
D
the placebo effect.
10

A trade school would like to measure the long-term success of its graduates after they leave the school, and emails a survey requesting information from graduates about their work experience. One question asks graduates if they are currently employed in the field they studied in school, while another asks them to share their annual salary. What type of bias is most likely to be present in the survey results?

A
This is voluntary response bias because graduates may choose to be part of the sample.
B
This is response bias because some graduates may not provide accurate information.
C
This is nonresponse bias because many graduates may choose not to respond to the email survey.
D
This is question wording bias because many graduates may misunderstand the questions asked.
11

A farmer plants a new type of corn and wants to quickly determine the yield, or total number of ears of corn, for the crop. He decides to take a simple random sample of the crop. He numbers each plant 1–100 and randomly picks 10 unique numbers. He then counts the number of ears of corn on these 10 plants and multiplies by 100. Which of the following statements is not true about the sample?

A
The sample of 10 plants was a census of the corn plants.
B
Each sample of 10 had an equal chance of being selected.
C
Each plant had an equal chance of being selected.
D
The sample of 10 plants was a simple random sample.
12

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

A
Systematic random sampling catches all patterns present in the population.
B
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.
C
Systematic random sampling can be used, even if knowledge of the entire population is not known.
D
Systematic random sampling requires a finite population size.
13

In an activity, students are pulling marbles from a large jar containing blue and red marbles. In their sample, students will calculate the proportion of red marbles. Which of the following is a correct statement about sampling variability?

A
The smaller the sample size of marbles, the smaller the sampling variability.
B
The larger the sample size of marbles, the larger the sampling variability.
C
The larger the sample size of marbles, the closer the sample proportion of red marbles will be to the true proportion of red marbles in the jar.
D
The smaller the sample size of marbles, the closer the sample proportion or red marbles will be to the true proportion of red marbles in the jar.
14

Researchers would like to assess the overall health of white pine trees in a state park. Using a computer program, the researchers selected 100 random points in the state park and assessed the trees closest to the selected points. Of the 100 trees selected, 24 showed damage to their lower limbs. Which of the following describes the population in this setting?

A
the 24 trees that show damage
B
all white pine trees in the state park
C
all white pine trees in the world
D
the 100 trees checked for damage
15

Randomization is important when assigning the students to the treatment and control groups to ensure

A
that the treatment group has more students to better test the hypothesis.
B
that both groups are made up of students from the same class.
C
that both groups are roughly equivalent with regards to students’ gender, reading ability, and study habits.
D
that each student does not know about the alternative version of the assignment.
16

Using the dotplot and the difference in mean ratings from the samples, is there convincing evidence that the one detergent is better than the other?

A
No, because a difference in mean rating of 1 point 5 or more occurred 23 out of 200 times, meaning the difference is not statistically significant and there is not convincing evidence that one brand is better than the other.
B
Yes, because a difference in mean rating of 1 point 5 or more occurred only 23 out of 200 times, meaning the difference is statistically significant and there is convincing evidence that cap b is more effective than cap A .
C
Yes, because a difference in mean rating of 1 point 5 or more occurred only 23 out of 200 times, meaning the difference is statistically significant and there is convincing evidence that cap A is more effective than cap b .
D
No, because a difference in mean rating of 1 point 5 or less occurred 167 out of 200 times, meaning the difference is not statistically significant and there is not convincing evidence that one brand is better than the other.
17

Which component is missing from the biologist’s process?

A
The biologist should have used random sampling when deciding which bats to catch.
B
The biologist did not randomly assign the bats to the treatment groups.
C
The biologist should have chosen a random night to catch the bats.
D
The biologist did not allow each bat the same chance to be in each treatment group.
18

Which of the following describes a completely randomized design for this experiment?

A
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.
B
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.
C
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.
D
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.

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