Chapter 4 Test STATS

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 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.

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.

You want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association (the largest teachers' union) and mail a questionnaire to 2500 teachers chosen at random from this list. In all, 1347 teachers return the questionnaire. 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

the 1347 teachers who mail back the questionnaire.

A marine biologist wants to estimate the mean size of the barnacle Semibalanus balnoides on a stretch ofrocky shoreline. To do so, he randomly selected twenty 10-cm. square plots and measured the size of everybarnacle 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.

Which of the following statements about a randomized complete block design with two treatments is not true?

B. Block A is chosen randomly from among the available experimental units.

For one kindergarten class in his district, a researcher determines which children already can read simple words and which children cannot upon entering kindergarten. The children are followed until third grade, at which point they are tested to determine the grade level at which they are reading. Those children who were reading simple words on entering kindergarten are found to be reading at a higher level than those who could not read simple words on entering kindergarten. The researcher a. can conclude that children should be taught to read in preschool, as there are clear benefits to reading early. b. cannot conclude that being able to read before entering kindergarten is beneficial, as there may be confounding variables in this study. c. needs to have taken a random sample of kindergarten students instead of one class to conclude a cause-and-effect relationship. d. needs to check the reading level of the children's parents. e. needs to retest in sixth grade or no conclusions can be reached.

B. cannot conclude that being able to read before entering kindergarten is beneficial, as there may be confounding variables in this study.

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

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.

random sample isScenario 4-3We wish to choose a simple random sample of size three from the following employees of a small company. To do this, we will use the numerical labels attached to the names below. a. 117. b. Bechhofer, Bechhofer again, and Taylor. c. Bechhofer, Taylor, Weiss. d. Kesten, Kiefer, Taylor. e. Taylor, Weiss, Ito.

C. Bechhofer, Taylor, Weiss.

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

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

Are dogs better at tracking the movements of brightly colored objects? Fifteen experienced "disk dogs" who have been trained to catch flying disks in mid-air are given the chance to catch a bright red disk or a plain white disk. Each disk is thrown 10 times for each dog, with the sequence of disks (red or white) determined randomly. The proportion of red disks caught to the proportion of white disks caught is compared for each dog. This is an example of a

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.

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 completely randomized design. e. A confounded, nonrandomized study.

A. A block design.

A candidate for mayor of Dallas calls 1,000 people chosen at random from the city telephone directory; 850 of them respond. What are the sampling frame and the sample in this example?

A. Sampling frame: the telephone directory. Sample: the 850 people who respond.

Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers randomly assigned 100 adult volunteers who suffer from allergies to two groups. They gave the new medication to the subjects in one group and an existing medication to the subjects in the other group. Forty-four percent of those in the treatment group and 28% of those in the control group reported a significant reduction in their allergy symptoms without any drowsiness. 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 sample was taken.

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.

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 another 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.

A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested ina new upscale men's clothing store. From a list of all residential addresses in Laramie, the firm selects asimple random sample of 100 and mails a brief questionnaire to each. The chance that all 100 homes in a particular neighborhood in Laramie end up being the sample of residential addresses selected is a. the same as for any other set of 100 residential addresses. b. exactly 0. Simple random samples will spread out the addresses selected.

A. the same as for any other set of 100 residential addresses.

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

When controlled experiments are impractical or unethical, which of the following would be necessary to establish a cause-and-effect relation between two variables?

E. All of the above.:Strong association between the variables.An association between the variables is observed in many different settings.The alleged cause is plausible.There is no obvious lurking variable that would affect the response variable

Simple random sampling

E. None of the above.

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.

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.

A farmer wishes to determine which of two brands of baby pig pellets, Kent or Moormans, produces better weight gains. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B.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 dependent variable.

c. the explanatory variable.

A lurking variable is

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

In the late 1990's Scotland was considering independence from England. An opinion poll showed that 51% of Scots favored "independence." Another poll taken at the same time showed that only 34% favored being "separate" from England. The reason these results differ by so much is that a. samples will usually differ just by chance due to random sampling. b. the wording of questions has a big effect on poll results. c. more follow-up efforts reduced the nonresponse rate of the second poll. d. the sample sizes are different, so the margins of error are different. e. the second poll suffered from under coverage.

b. the wording of questions has a big effect on poll results.

Use Scenario 4-4. The first three students in your sample have labels a. 955, 929, 400. b. 400, 769, 769. c. 559, 294, 007. d. 929, 400, 769. e. 400, 769, 335.

e. 400, 769, 335.

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.

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" (two cups of coffee) and all students in the 9:30 section are not permitted to have any caffeine before a mid-term exam. 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.

A sportswriter wants to know how strongly Lafayette residents support the local minor league baseball team, the Lafayette Leopards. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. What is the intended population for the survey?A. all American adultsB. all people attending the game the day the survey was conductedC. all Leopard fansD. the 20 people who gave the sportswriter their opinionE. all residents of Lafayette

E. All residents of Lafayette

Use Scenario 4-3. Which of these statements about the table of random digits is true?Scenario 4-3We wish to choose a simple random sample of size three from the following employees of a small company. To do this, we will use the numerical labels attached to the names below. a. Every row must have exactly the same number of 0's and 1's. b. In the entire table, there are exactly the same number of 0's and 1's. c. If you look at 100 consecutive pairs of digits anywhere in the table, exactly 1 pair is 00. d. All of these are true. e. None of these is true.

E. None of these is true.

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.

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'sheart 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 subjectperformed 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 "stepheight" are the a. factors. b. levels. c. controls. d. units. e. response variables.

A. factors.

A sportswriter wants to know how strongly Lafayette residents support the local minor league baseball team, the Lafayette Leopards. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. The newspaper asks you to comment on their survey of a local opinion. You say: A. This is a census, because all fans had a chance to be asked. It gives very accurate results B. This is a SRS. The results are not biased, but the sample is too small to have high precision C. This is a convenience sample. It will almost certainly underestimate the level of support among all Lafayette residents D. This is a convenience sample. It will almost certainly overestimate the level of support among all Lafayette residentsE. This is a SRS, it gives very accurate results.

D. This is a convenience sample. It will almost certainly overestimate the level of support among all Lafayette residents.

In order to assess the effects of exercise on reducing cholesterol, a researcher took a random sample of fifty people from a local gym who exercised regularly and another random sample of fifty people from the surrounding community who did not exercise regularly. They all reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether or not subjects exercised regularly. Which of the following best describes the inferences the researcher can make based in his results?

E. There is not enough information to make judgments about the scope of inference.

An opinion research firm wants to find the country's reaction to a speech by a famous politician. They randomly select six states, then randomly select ten Zip Codes from each state. Fifty people from each Zip Code are randomly selected for the survey. This is an example of a. convenience sampling. b. cluster sampling. c. stratified random sampling. d. simple random sampling. e. multistage sampling.

E. multistage sampling.