AP Statistics Chapter 4 Multiple Choice Questions

Control groups are used in experiments in order to accomplish which one of the following? (a) Control the effects of outside variables on the outcome. (b) Control the subjects of a study to ensure that all participate equally. (c) Guarantee that someone other than the investigators, who have a vested interest in the outcome, controls how the experiment is conducted. (d) Achieve a proper and uniform level of randomization. (e) Reduce variability in results.

(a) Control the effects of outside variables on the outcome.

To test the effect of music on productivity, a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is (a) an observational study. (b) a matched pairs experiment. (c) a completely randomized experiment. (d) a block design, but not a matched pairs experiment. (e) impossible to classify unless more details of the study are provided.

(b) a matched pairs experiment.

A researcher observes that, on average, the number of divorces in cities with Major League Baseball teams is larger than in cities without Major League Baseball teams. Which of the following is the most plausible explanation for this observed association? (a) The presence of a Major League Baseball team causes the number of divorces to rise (perhaps husbands are spending too much time at the ballpark). (b) The high number of divorces is responsible for the presence of Major League Baseball teams (more single men means potentially more fans at the ballpark, making it attractive for an owner to relocate to such cities). (c) The association is due to a lurking variable (Major League teams tend to be in large cities with more people, hence a greater number of divorces). (d) The association makes no sense, since many married couples go to the ballpark together. (e) The association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental.

(c) The association is due to a lurking variable (Major League teams tend to be in large cities with more people, hence a greater number of divorces).

A researcher for a consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that will use the company's current detergent formula. The most important reason for this random assignment is that (a) randomization makes the analysis easier since the data can be collected and entered into the computer in any order. (b) randomization eliminates the impact of any confounding variables. (c) randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups. (d) randomization ensures that the study is double-blind. (e) randomization reduces the impact of outliers.

(c) randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups.

A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and made by companies based in Japan. A simple random sample of 25 cars from a parking lot at LeeDavis High School was taken. Which of the following statements is correct? (a) Since this is a simple random sample, it should be representative of all the cars in Mechanicsville. (b) If a simple random sample of 15 cars were taken, we would expect the same amount of variability in the proportion of red cars as we would with a sample of 25 cars. (c) An alternative method for getting a representative sample would be to select the 25 cars closest to a specified location, such as the entrance to the gymnasium. (d) A different team doing the sampling independently would probably obtain a slightly different answer for their sample proportion. (e) The results would be the same regardless of the time of day that the sample is taken.

(d) A different team doing the sampling independently would probably obtain a slightly different answer for their sample proportion.

A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively: (a) A specific storage time, amount of vitamin C, a fruit pack (b) A fruit pack, amount of vitamin C, a specific storage time (c) Random assignment, a fruit pack, amount of vitamin C (d) A specific storage time, a fruit pack, amount of vitamin C (e) A specific storage time, six fruit packs, amount of vitamin C

(d) A specific storage time, a fruit pack, amount of vitamin C

A survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salaries of women and men. For a random sample of graduates, three variables are to be recorded: sex, starting salary, and area of specialization. Which of the following best describes a conclusion that can be drawn from this study? (a) Whether being female causes graduates of this nursing school to have lower (or higher) starting salaries than males. (b) Whether being female causes graduates in this sample to have lower (or higher) starting salaries than males. (c) Whether choosing a certain area of specialization causes females graduates of this nursing school to have lower (or higher) starting salaries than males. (d) Whether there is an association between sex and starting salary among graduates of this nursing school. (e) Whether there is an association between sex and starting salary at all nursing schools.

(d) Whether there is an association between sex and starting salary among graduates of this nursing school.

A maple sugar manufacturer wants to estimate the average trunk diameter of Sugar Maples trees in a large forest. There are too many trees to list them all and take a SRS, so he divides the forest into several hundred 10 meter by 10 meter plots, selects 25 plots at random, and measures the diameter of every Sugar Maple in each one. This is an example of a (a) multistage sample. (b) stratified sample. (c) simple random sample. (d) cluster sample. (e) convenience sample.

(d) cluster sample.

Eighty volunteers who currently use a certain brand of over-the-counter allergy medication have been recruited to participate in a trial of a new allergy medication. The volunteers are randomly assigned to one of two groups. One group continues to take their current medication, the other group switches to the new experimental medication. Each is asked after two weeks if their allergy symptoms are worse, better, or about the same as they were at the start of the study. Which of the follow best describes a conclusion that can be drawn from this study? a) We can determine whether the new drug reduces symptoms more than the old drug for anyone who suffers from allergies. b) We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study. c) We can determine whether the allergies sufferers' symptoms improved more with the new drug than with the old drug, but we can't establish cause and effect. d) We cannot draw any conclusions, since all the volunteers were already taking the old drug when the experiment started. e) We cannot draw any conclusions, because there was no control group.

b) We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study.

To test the effects of a new fertilizer, 100 plots were divided in half. Fertilizer A is randomly applied to one half, and B to the other. This is a) an observational study. b) a matched pairs experiment. c) a completely randomized experiment. d) a block design, but not a matched pairs experiment. e) impossible to classify unless more details of the study are provided.

b) a matched pairs experiment.

According to the 1990 census, those states with an above-average number of people X, who fail to complete high school tend to have an above average number of infant deaths, Y. In other words, there is a positive association between X and Y. The most plausible explanation for this is a) X causes Y. Programs to keep teens in school will help reduce the number of infant deaths. b) Y causes X. Programs that reduce infant deaths will ultimately reduce high school dropouts. c) Other variables may be confounded with variable X. For example, states with large populations may have both larger numbers of people who don't complete high school and more infant deaths. d) Both of these variables are directly affected by the higher incidence of cancer in certain states. e) The association between X and Y is purely coincidental.

c) Other variables may be confounded with variable X. For example, states with large populations may have both larger numbers of people who don't complete high school and more infant deaths.

You work for an advertising agency that is preparing a new television commercial to appeal to women. You have been asked to design an experiment to compare the effectiveness of three versions of the commercial. Each subject will be shown one of the three versions and then asked her attitude toward the product. You think there may be large differences between women who are employed outside the home and those who are not. Because of these differences, you should use a) a completely randomized design. b) a categorical variable. c) a block design. d) a stratified design. e) a multistage sample.

c) a block design.

An airline that wants to assess customer satisfaction chooses a random sample of 10 of its flights during a single month and asks all of the passengers on those flights to fill out a survey. This is an example of a a) multistage sample. b) stratified sample. c) cluster sample. d) simple random sample. e) convenience sample.

c) cluster sample.

There are ten departments at SMART University. To conduct a survey, a researcher selects ten faculty members randomly from each department. The sample selected in this way is called a: a. Simple random sample. b. Systematic sample. c. Stratified random sample. d. Voluntary response sample. e. Multistage sample.

c. Stratified random sample.

A polling agency took a random sample of 1000 likely voters in Florida (population: about 18 million), and another random sample of 1000 likely voters in New Mexico (population: about 2 million). Other things being equal, the sample from Florida would tend to be ___________ as the sample from New Mexico. a. 9 times as accurate b. 3 times as accurate c. as accurate d. one third as accurate e. one ninth as accurate

c. as accurate

There are two statistics classes. The first has 350 students and the second has 250 students. In the first class the students are instructed to each toss a coin 20 times and record the value of p$ , the proportion of heads. The instructor them makes a histogram of the 350 values of p$ obtained. The second class did the same, except that each student tossed a coin 40 times. The histogram of p$ values for the first class should be a. more biased since it is based on a smaller number of tosses. b. less biased since it is based on a larger number of students. c. more variable since it is based on a smaller number of tosses. d. less variable since it is based on a larger number of students.

c. more variable since it is based on a smaller number of tosses.

A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude: a. that the remedy is effective for the treatment of headaches. b. nothing, because the sample size is too small. c. nothing, because there is no control group for comparison. d. that the new treatment is better than aspirin. e. that the remedy is not effective for the treatment of headaches.

c. nothing, because there is no control group for comparison.

In an experiment to measure the effect of fluoride "varnish" on the incidence of tooth cavities, 34 10-year-old-girls whose parents volunteered them for the study were randomly assigned to two groups. One group was given fluoride varnish annually for 4 years along with a standard dental hygiene regimen; the other group only followed the standard dental hygiene regimen. The mean number of cavities in the two groups was compared at the end of the treatments. Which of the following is a problem with this experiment? a) Since the subjects were not randomly selected for the study, we cannot conclude that a reduction in cavities can be attributed to the fluoride treatment. b) There was no control group. c) The absence of replication increases the impact of random variation. d) There was insufficient attention to the placebo effect. e) The experimental subjects should not have been limited to girls.

d) There was insufficient attention to the placebo effect.

The following numbers appear in a table of random digits: 38683 50279 38224 09844 13578 28251 12708 24684 A scientist will be measuring the total amount of leaf litter in a random sample (n = 5) of forest sites selected without replacement from a population of 45 sites. The sites are labeled 01, 02, . . . , 45 and she starts at the beginning of the line of random digits and takes consecutive pairs of digits. Which of the following is correct? a) Her sample is 38, 25, 02, 38, 22 b) Her sample is 38, 68, 35, 02, 22 c) Her sample is 38, 35, 27, 28, 08 d) Her sample is 38, 65, 35, 02, 79 e) Her sample is 38, 35, 02, 22, 40

e) Her sample is 38, 35, 02, 22, 40