ch 4 stats

____ 45. 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

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

____ 42. 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.

____ 18. A stratified random sample addresses the same issues as which of the following experimental designs?

A. A block design.

A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested in a new upscale men's clothing store. From a list of all residential addresses in Laramie, the firm selects a simple 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.

____ 46. 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.

____ 20. 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

B. cluster sampling

____ 17. A stratified random sample is appropriate when

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.

____ 9. A simple random sample of size n is defined to be

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.

____ 39. The principle reason for replication in designing experiments is that it

C. reduces sampling variability.

____ 41. In an experiment, an observed effect so large that it would rarely occur by chance is called

C. statistically significant.

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

D. a convenience sample

____ 50. 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.

____ 25. 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

D. nonresponse.

____ 19. 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

D. stratified random sampling

____ 32. A lurking variable is

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

____ 48. 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.

____ 14. Use Scenario 4-3. The simple random sample is Scenario 4-3 We 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.

C. Bechhofer, Taylor, Weiss.

____ 12. Simple random sampling

E. None of the above.

____ 1. Use Scenario 4-1. The intended population for this survey is: Scenario 4-1 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.

all residents of Lafayette

____ 2. Use Scenario 4-1. The sample for the survey is Scenario 4-1 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 20 people who gave the sportswriter their opinion

____ 40. 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

____ 27. The essential difference between an experiment and an observational study is that

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

____ 13. An example of a nonsampling error that can reduce the accuracy of a sample survey is

E. many members of the sample cannot be contacted.

22. 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

E. multistage sampling.

____ 3. Use Scenario 4-1. The newspaper asks you to comment on their survey of local opinion. You say: Scenario 4-1 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.

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

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.

____ 43. A double-blind experiment was conducted to evaluate the effectiveness of the Salk polio vaccine. The purpose of keeping the diagnosing physicians ignorant of the treatment status of the experimental subjects was to

C. eliminate a possible source of bias.

____ 15. Use Scenario 4-3. Which of the following statements is true? Scenario 4-3 We 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.

D. If we use another list of random digits to select the sample, the result obtained with the list actually used would be just as likely to be selected as any other set of three names.

____ 33. 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?

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

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

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

____ 37. The principle reason for the use of random assignment in designing experiments is that it

D. creates approximately equal groups for comparison.

____ 49. 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

D. matched pairs design.

____ 31. Medical researchers are excited about a new cancer treatment that destroys tumors by cutting off their blood supply. To date, the treatment has only been tried on mice, but in mice it has been nearly 100% effective in eradicating tumors and appears to have no side effects. As evidence of the effectiveness of the new treatment in treating cancer in humans, these studies

D. suffer from lack of realism.

____ 16. Use Scenario 4-3. Which of these statements about the table of random digits is true? Scenario 4-3 We 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.

E. None of these is true.

____ 47. The reason that blocking (as in a randomized block design) is sometimes used in experimentation is to

E. reduce variability arising from random assignment.

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.

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.

____ 38. 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.

____ 30. 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.

____ 26. Which of the following is not a major principle of good design for all experiments?

C. Blocking

____ 11. A simple random sample is

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

____ 44. 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.

____ 34. 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.

____ 36. 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

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

23. 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

B. cluster sampling.

____ 29. The most important advantage of experiments over observational studies is that

B. experiments can give better evidence of causation.

____ 35. 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

C. confounding.

____ 24. A local tax reform group polls the residents of the school district and asks the question, "Do you think the school board should stop spending taxpayers' money on non-essential arts programs in elementary schools?" The results of this poll are likely to

B. Underestimate support for arts programs because of nonsampling error.

____ 21. In order to select a sample of undergraduate students in the United States, I select a simple random sample of four states. From each of these states, I select a simple random sample of two colleges or universities. Finally, from each of these eight colleges or universities, I select a simple random sample of 20 undergraduates. My final sample consists of 160 undergraduates. This is an example of

C. multistage sampling.

__ 28. 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

B. which brand they prefer.