AnswersNC-Math 4 CRUnit Test

Unit Test — Unit test Answers

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1
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A florist wants to determine if a new additive would extend the life of cut flowers longer than the original additive. The florist selects the first 20 carnations from the ones recently delivered by the greenhouse and assigns the first 10 to the new additive and the rest to the original additive. After three weeks, 6 carnations placed in the new additive still looked healthy, and 2 carnations placed in the original additive still looked healthy. The proportion of healthy carnations with the new additive was significantly greater than the proportion of healthy carnations with the original additive.

A
It can be inferred that the new additive caused the extended life of the cut flowers, and this inference can be applied to all carnations.
B
It cannot be inferred that the new additive caused the extended life of the cut flowers, and this inference cannot be applied to the carnations from the greenhouse.
C
It can be inferred that the new additive caused the extended life of the cut flowers, and this inference can only be applied to the carnations from the greenhouse.
D
It cannot be inferred that the new additive caused the extended life of the cut flowers, and this inference can only be applied to the carnations from the greenhouse.
2
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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.

A
that both groups are made up of students from the same class.
B
that the treatment group has more students to better test the hypothesis.
C
that each student does not know about the alternative version of the assignment.
D
that both groups are roughly equivalent with regards to students’ gender, reading ability, and study habits.
3

A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers placed an ad online asking volunteers to participate in the study, and 100 subjects replied. They are informed that one group will receive a new cream and the other group will receive a cream with no active ingredient. The researchers believe that sun exposure may affect the cream’s effectiveness. The subjects are then asked about their outdoor activity, and 42 of the subjects state they spend more than 50% of their day outside. The 42 subjects are randomly assigned to the two treatments. The remaining 58 subjects are also randomly assigned to the two treatments. All subjects are exposed to poison ivy and given their cream. They are asked to return in three days and report their level of irritation.

A
Yes, the subjects could be randomly assigned to two different treatments.
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
No, the subjects were not paired by age to determine if it affected the cream’s effectiveness.
4

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?

A
type of vehicle
B
year of vehicle
C
make of the vehicle
D
color of the vehicle
5

A biologist wonders if the life span of bats will be affected by two new food sources from invasive species moving into an area. To conduct the experiment, the biologist needs three treatment groups: a group where the diet will not include invasive species (control), a group where the diet will include one invasive species (treatment group 1), and another group where the diet will include the other invasive species (treatment group 2). The biologist chooses the first cloud-free night and catches the first 18 bats that fly out of a cave. The first six bats will be the control group, the second six will be treatment group 1, and the last six will be treatment group 2.

A
The biologist should have chosen a random night to catch the bats.
B
The biologist did not randomly assign the bats to the treatment groups.
C
The biologist did not allow each bat the same chance to be in each treatment group.
D
The biologist should have used random sampling when deciding which bats to catch.
6

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.

Question illustration
A
00, 29, 90, 75, 71, 17, 37, 76
B
29, 17, 37, 48, 20, 48, 27, 12
C
2, 9, 7, 5, 1, 3, 6, 4
D
29, 17, 37, 48, 20, 27, 12, 23
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% 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%.
B
The survey suffers from voluntary response bias and may not accurately represent the population.
C
Only 362 responses cannot provide a suitable estimate of families who own their home.
D
The survey suffers from undercoverage and may not provide a suitable estimate of homeownership.
8

A researcher is comparing the effectiveness of three devices designed to help people who snore. There are 120 people who snore participating in the experiment. Using a table of random digits, the researcher will randomly place the participants into three equally sized treatment groups suitable for comparison.

A
3
B
40
C
80
D
120
9

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 larger the sample size of marbles, the larger the sampling variability.
B
The smaller the sample size of marbles, the smaller 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.
10

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?

A
The survey will provide a reasonable estimate of mean annual salary because all graduates were sent the email survey.
B
The survey will likely overestimate mean annual salary because those with higher salaries may be more likely to respond to the survey.
C
The survey will likely underestimate mean annual salary because there may be more graduates with lower salaries than higher salaries.
D
The survey will likely overestimate the mean annual salary because the email was only sent to graduates with jobs in their chosen field.
11

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.

A
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.
B
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.
C
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.
D
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.
12

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.

A
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.
B
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.
C
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.
D
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.
13

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.

A
Method 1 is an observational study because past data are collected and analyzed.
B
Method 2 is an observational study because two city schools are chosen to participate.
C
Method 2 is an observational study because students can choose to participate in the music lessons.
D
Both methods are observational studies because both include students who do and do not play a musical instrument.
14

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.

A
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.
B
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.
C
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.
D
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.
15

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.

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

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