AP Statistics Chapter 4 Test

In an experiment, an observed effect so large that it would rarely occur by chance is called A. an outlier. B. influential. C. statistically significant. D. bias. E. replication.

C. statistically significant.

Use Scenario 4-7. The farmer has conducted a(n) A. stratified random sample. B. matched pairs design. C. observational study. D. experiment, but not a completely randomized experiment. E. completely randomized experiment.

D. experiment, but not a completely randomized experiment.

Use Scenario 4-8. Which of the following best describes the inferences the researchers can make based in his results? A. They can make inferences about cause and effect, but not about the populations from which the samples were taken. B. They can make inferences about the populations from which the samples were taken, but not about cause and effect. C. They can make inferences about both cause and effect and the populations from which the samples were taken. D. They cannot make inferences about either cause and effect or the populations from which the samples were taken. E. There is not enough information to make judgments about the scope of inference.

A. They can make inferences about cause and effect, but not about the populations from which the samples were taken.

A lurking variable is A. a variable that is not among the variables studied but that affects the response variable. B. the true cause of a response. C. any variable that produces a large residual. D. the true variable that is explained by the explanatory variable. E. another response variable.

A. a variable that is not among the variables studied but that affects the response variable.

A television station is interested in predicting whether voters in its viewing area are in favor of offshore drilling. It asks its viewers to phone in and indicate whether they support/are in favor of or are opposed to this practice. Of the 2241 viewers who phoned in, 1574 (70%) were opposed to offshore drilling. The viewers who phoned in are A. a voluntary response sample. B. a convenience sample. C. a probability sample. D. a population. E. a simple random sample.

A. a voluntary response sample.

A study of elementary school children, ages 6 to 11, finds a high positive correlation between shoe size x and score y on a test of reading comprehension. The observed correlation is most likely due to A. the effect of a lurking variable, such as age. B. a mistake, since the correlation must be negative. C. cause and effect (larger shoe size causes higher reading comprehension). D. "reverse" cause and effect (higher reading comprehension causes larger shoe size. E. several outliers in the data set.

A. the effect of a lurking variable, such as age.

Use Scenario 4-6. Instead of giving all students in the 8:30 section two cups of coffee, students in the 8:30 section are randomly assigned to a treatment group (two cups of coffee. or a control group (two cups of decaffeinated coffee). The coffee is so bad that students cannot tell whether they are in the treatment or the control group. As it turns out, students in both groups do better on the exam than students in the 9:30 section, who weren't given anything. This could be the result of A. the placebo effect. B. an observational study. C. voluntary response. D. sampling variability. E. all of the above.

A. the placebo effect.

A market research company wishes to find out whether the population of students at a university prefers brand A or brand B of instant coffee. A random sample of students is selected, and each one is asked to try brand A first and then brand B (or vice versa, with the order determined at random). They then indicate which brand they prefer. The response variable is A. whether brand A or B is tried first. B. which brand they prefer. C. the two brands of coffee. D. the identity of the student. E. none of these.

B. which brand they prefer.

Which of the following is not a major principle of good design for all experiments? A. Comparison to a control. B. Replication C. Blocking D. Randomization E. All of these are important principles for every experiment.

C. Blocking

A stratified random sample is appropriate when A. It is impractical to take a simple random sample because the population is too large. B. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is quite different within the groups but very similar between groups. C. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups. D. You intend to take a sample of more than 100 individuals. E. You want to avoid undercoverage of certain groups.

C. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups.

The principle reason for replication in designing experiments is that it A. distinguishes a treatment effect from the effects of confounding variables. B. allows double-blinding. C. reduces sampling variability. D. creates approximately equal groups for comparison. E. eliminates the placebo effect.

C. reduces sampling variability.

Just before the presidential election of 1936, the magazine Literary Digest predicted—incorrectly, as it turned out—that Alf Landon would defeat Franklin Delano Roosevelt. Landon lost in a landslide. It turned out that the magazine had only polled its own subscribers, plus others from a list of automobile owners and a list of people who had telephone service. All three groups had higher than typical incomes during the Great Depression. This is an example of A. voluntary response bias. B. bias resulting from question wording. C. undercoverage. D. nonresponse. E. response bias.

C. undercoverage.

An experiment compares the taste of a new spaghetti sauce with the taste of a commercially successful sauce readily available in grocery stores. Each of a number of tasters tastes both sauces (in random order) and says which tastes better. This is called a A. simple random sample. B. stratified random sample. C. completely randomized design. D. matched pairs design. E. double-blind design.

D. matched pairs design.

Frequently, telephone poll-takers call near dinner time—between 6 pm and 7 pm—because most people are at home them. This is an effort to avoid A. voluntary response bias. B. calling people after they have gone to bed. C. a convenience sample. D. nonresponse. E. response bias.

D. nonresponse.

We divide the class into two groups: first year students and others. We then take random samples from each group. This is an example of A. simple random sampling B. cluster sampling C. multistage sampling D. stratified random sampling E. systematic random sampling

D. stratified random sampling

Use Scenario 4-6. Suppose half of the 8:30 students are randomly allocated to the treatment group (two cups of coffee), the other half to the control group (two cups of decaf). In addition, half of the 9:30 students are randomly allocated to the treatment group, the other half to the control group. This is an example of a A. voluntary response study. B. stratified sampling procedure. C. matched pairs design. D. completely randomized design. E. block design.

E. block design.

Use Scenario 4-6. The response variable in this study is A. two cups of coffee. B. the time the class is held. C. class attendance. D. teacher's performance. E. exam performance.

E. exam performance.

The essential difference between an experiment and an observational study is that A. observational studies may have confounded variables, but experiments never do. B. in an experiment, people must give their informed consent before being allowed to participate. C. observational studies are always biased. D. observational studies cannot have response variables. E. an experiment imposes treatments on the subjects, but an observational study does not.

E.. an experiment imposes treatments on the subjects, but an observational study does not.

Use Scenario 4-5. This is a(n) A. observational study. B. experiment, but not a double blind experiment. C. double blind experiment. D. matched pairs experiment. E. block design.

A. observational study.

Use Scenario 4-2. The sample is A. the 1347 teachers who mail back the questionnaire. B. the 2500 teachers to whom you mailed the questionnaire. C. all members of the National Education Association. D. all American school teachers. E. all American school students.

A. the 1347 teachers who mail back the questionnaire.

In comparative trials in medicine, the placebo effect and subconscious bias on the part of the physicians evaluating treatment outcomes can be avoided by using A. the double-blind technique. B. randomized complete block designs. C. response variables. D. stratified random samples. E. all of the above.

A. the double-blind technique.

Use Scenario 4-7. The brand of pellets is A. a parameter. B. the response variable. C. the explanatory variable. D. the placebo effect. E. a lurking variable.

C. the explanatory variable.

Use Scenario 4-7. If the farmer had fed Kent pellets to an SRS of 5 pigs from litter A and an SRS of 5 pigs from litter B, with the remaining 10 pigs getting Moormans pellets, then he would have been using A. a systematic random sample. B. a convenience sample. C. a matched-pairs design. D. a block design. E. a completely randomized design.

D. a block design.

A stratified random sample addresses the same issues as which of the following experimental designs? A. A block design B. A double-blind experiment. C. An experiment with a placebo. D. A matched pairs design. E. A confounded, nonrandomized study.

A. A block design

A news release for a diet products company reports: "There's good news for the 65 million Americans currently on a diet." Its study showed that people who lose weight can keep it off. The sample was twenty graduates of the company's program who endorse it in commercials. The results of the study are probably A. biased, overstating the effectiveness of the diet. B. biased, understating the effectiveness of the diet. C. unbiased because these are nationally recognized individuals. D. unbiased, but they could be more accurate. A larger sample size should be used. E. biased, but it is hard to tell whether the results will overstate or understate the effects of the diet.

A. biased, overstating the effectiveness of the diet.

Use Scenario 4-7. The feed they get is not the only factor affecting the rate at which pigs gain weight. Genetic differences also affect weight gain. It is likely that the pigs in litter A are genetically different from the pigs in litter B, since the two litters have different mothers. Since the farmer is only interested in determining which brand of pellets is better, the study suffers from A. confounding. B. common response. C. convenience sampling. D. invalid measurement. E. experimenter bias.

A. confounding.

The principle reason for the use of controls in designing experiments is that it A. distinguishes a treatment effect from the effects of confounding variables. B. allows double-blinding. C. reduces sampling variability. D. creates approximately equal groups for comparison. E. eliminates the placebo effect.

A. distinguishes a treatment effect from the effects of confounding variables.

An experiment was conducted by some students to explore the nature of the relationship between a person's heart rate (measured in beats per minute) and the frequency at which that person stepped up and down on steps of various heights. Three rates of stepping and two different step heights were used. A subject performed the activity (stepping at one of the three stepping rates at one of the two possible heights) for three minutes. Heart rate was then measured at the end of this period. The variables "stepping rate" and "step height" are the A. factors. B. levels. C. controls. D. units. E. response variables.

A. factors.

One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other fifty are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of the depression. The factor in this study is A. which treatment the volunteers receive. B. the extent to which the depression was reduced. C. the use of randomization and the fact that this was a comparative study. D. the use of a psychiatrist to evaluate the severity of depression. E. the symptoms observed by the psychiatrist.

A. which treatment the volunteers receive.

Use Scenario 4-8. The experimental units are the A. researchers. B. 100 adult volunteers. C. all the volunteers who reported a significant reduction in their allergy symptoms without any drowsiness. D. all the volunteers who did not report a significant reduction in their allergy symptoms without any drowsiness. E. pills containing the new experimental medication.

B. 100 adult volunteers.

Use Scenario 4-5. Which of the following best describes the inferences the researcher can make based in his results? A. He can make inferences about cause and effect, but not about the populations from which the samples were taken. B. He can make inferences about the populations from which the samples were taken, but not about cause and effect. C. He can make inferences about both cause and effect and the populations from which the samples were taken. D. He cannot make inferences about either cause and effect or the populations from which the samples were taken. E. There is not enough information to make judgments about the scope of inference.

B. He can make inferences about the populations from which the samples were taken, but not about cause and effect

To determine the proportion of each color of Peanut Butter M&M, you buy 10 1.69 ounce packages and count how many there are of each color. This is an example of A. simple random sampling B. cluster sampling C. multistage sampling D. stratified random sampling E. systematic random sampling

B. cluster sampling

A marine biologist wants to estimate the mean size of the barnacle Semibalanus balnoides on a stretch of rocky shoreline. To do so, he randomly selected twenty 10-cm. square plots and measured the size of every barnacle in each plot. This is an example of A. convenience sampling. B. cluster sampling. C. stratified random sampling. D. simple random sampling. E. multistage sampling.

B. cluster sampling.

The most important advantage of experiments over observational studies is that A. experiments are usually easier to carry out. B. experiments can give better evidence of causation. C. confounding cannot happen in experiments. D. an observational study cannot have a response variable. E. observational studies cannot use random samples.

B. experiments can give better evidence of causation.

A public opinion poll in Ohio wants to determine whether or not registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of fifty registered voters from each county in the state and ask whether they approve or disapprove of the measure. This is an example of a A. systematic random sample. B. stratified random sample. C. multistage sample. D. simple random sample. E. cluster sample.

B. stratified random sample.

Use Scenario 4-7. The weight of the pigs after four weeks is A. a parameter. B. the response variable. C. the explanatory variable. D. the placebo effect. E. stratified.

B. the response variable.

Twelve people who suffer from chronic fatigue syndrome volunteer to take part in an experiment to see if shark fin extract will increase one's energy level. Eight of the volunteers are men, and four are women. Half of the volunteers are to be given shark fin extract twice a day, and the other half are to be given a placebo twice a day. We wish to make sure that four men and two women are assigned to each of the treatments, so we decide to use a block design with the men forming one block and the women the other. A block design is appropriate in this experiment if A. we want to be able to compare effects on energy level in men and women. B. we believe men and women will respond differently to treatments. C. gender equity is an important legal consideration in this study. D. we want the conclusions to apply equally to men and women. E. all of the above.

B. we believe men and women will respond differently to treatments.

A simple random sample of size n is defined to be A. a sample of size n chosen in such a way that every unit in the population has the same chance of being selected. B. a sample of size n chosen in such a way that every unit in the population has a known nonzero chance of being selected. C. a sample of size n chosen in such a way that every set of n units in the population has an equal chance to be the sample actually selected. D. a sample of size n chosen in such a way that each selection is made independent of every other selection. E. all of the above. They are essentially identical definitions.

C. a sample of size n chosen in such a way that every set of n units in the population has an equal chance to be the sample actually selected.

A simple random sample is A. any sample selected by using chance. B. any sample that gives every individual the same chance to be selected. C. a sample that gives every possible sample of the same size the same chance to be selected. D. a sample that selects equal numbers of individuals from each stratum. E. a sample that contains the same percent of each subgroup in the population.

C. a sample that gives every possible sample of the same size the same chance to be selected.

If changes in a response variable are due to the effects of the explanatory variable as well as the effects of lurking variables, and we cannot distinguish between these effects, we are said to have A. a cause-and-effect relation between the explanatory and response variable. B. a placebo effect. C. confounding. D. correlation. E. extrapolated.

C. confounding.

Use Scenario 4-6. Unfortunately, any systematic difference between the two sections on the exam might be due to the fact that the 8:30 and 9:30 classes have different instructors. This is an example of A. placebo effect. B. bias. C. confounding. D. observational study. E. stratification.

C. confounding.

One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other fifty are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of the depression. The study would be double blind if A. neither drug had any identifying marks on it. B. all volunteers were not allowed to see the psychiatrist nor the psychiatrist allowed to see the volunteers during the session in which the psychiatrist evaluated the severity of the depression. C. neither the volunteers nor the psychiatrist knew which treatment any person had received. D. the patients were given a placebo. E. all of the above.

C. neither the volunteers nor the psychiatrist knew which treatment any person had received.

The owner of a chain of supermarkets notices that there is a positive correlation between the sales of beer and the sales of ice cream over the course of the previous year. During seasons when sales of beer were above average, sales of ice cream also tended to be above average. Likewise, during seasons when sales of beer were below average, sales of ice cream also tended to be below average. Which of the following would be a valid conclusion from these facts? A. Sales records must be in error. There should be no association between beer and ice cream sales. B. Evidently, for a significant proportion of customers of these supermarkets, drinking beer causes a desire for ice cream or eating ice cream causes a thirst for beer. C. A scatterplot of monthly ice cream sales versus monthly beer sales would show that a straight line describes the pattern in the plot, but it would have to be a horizontal line. D. It is likely that sales of both beer and ice cream are confounded with a lurking variable, such as seasonal variation in temperature. E. There is a clear, negative association between beer sales and ice cream sales.

D. It is likely that sales of both beer and ice cream are confounded with a lurking variable, such as seasonal variation in temperature.

In order to assess the opinion of students at the University of Minnesota on campus snow removal, a reporter for the student newspaper interviews the first 12 students he meets who are willing to express their opinion. The method of sampling used is A. a census B. a systematic sample C. a voluntary sample D. a convenience sample E. a simple random sample

D. a convenience sample

A study sponsored by American Express Co. and the French government tourist office found that old stereotypes about French unfriendliness were not true. The respondents were more than 1000 Americans who have visited France more than once for pleasure over the past two years. The results of this study are probably A. very accurate, given the large sample size. B. very inaccurate because the sample is only a small fraction of all Americans who have visited France. C. extremely variable, because people's opinions differ so greatly. D. biased, overstating the extent to which the old stereotypes were not true. E. biased, understating the extent to which the old stereotypes were not true.

D. biased, overstating the extent to which the old stereotypes were not true.

The principle reason for the use of random assignment in designing experiments is that it A. distinguishes a treatment effect from the effects of confounding variables. B. allows double-blinding. C. reduces sampling variability. D. creates approximately equal groups for comparison. E. eliminates the placebo effect.

D. creates approximately equal groups for comparison.