University of South Carolina
CHAPTER 1? Which of the variables is not considered to be numerical?AnswerA.The type of operating systemB.The year purchasedC.the number of Brian's classmatesD.The amount of memoryQuestionWhat is the difference between a census and a sample survey?AnswerA.A census attempts to include the entire population in the survey whereas a sample survey only studies some of the members of the population.?B.A census looks at a larger group than a sample survey to gather information about the population.C.A census can study many variables whereas a sample survey can only study one or two.D.A census can only be conducted by a government whereas a sample survey can be conducted by anyone.QuestionConsider the three situations:I. You ask a sample of doctors about the health risks involved with going out in the cold without a jacket.II. On cold days, you record which of your classmates come to school without a jacket. Later, you record how many of those students become sick. You take notes and observe at a local gym your fellow members who go outside with a wet head and notice if they are sick when they return to the gym at a later date.III. You find 30 adults and divide them into two groups. The first group is told not to wear jackets on cold days, the other group is told to wear jackets on cold days.You then compare the number from each group who get sick after a string of cold days.Which of the following situations is an example of an observational study?AnswerA.Situation IIB.Situation IC.Situation III QuestionConsider the three situations:I. You ask a sample of doctors about the health risks involved with going out in the cold without a jacket.II. On cold days, you record which of your classmates come to school without a jacket. Later, you record how many of those students become sick. You take notes and observe at a local gym your fellow members who go outside with a wet head and notice if they are sick when they return to the gym at a later date.III. You find 30 adults and divide them into two groups. The first group is told not to wear jackets on cold days, the other group is told to wear jackets on cold days.You then compare the number from each group who get sick after a string of cold days.Which of the following situations is an example of an experiment? ????AnswerA.Situation IIIB.Situation IC.Situation IIQuestionThe Nielsen television ratings is an example of a:AnswerA.ExperimentB.PopulationC.CensusD.Sample Survey QuestionThe difference between an experiment and an observational study is:AnswerA.An observational study tries to gather information without interfering; an experiment looks to actively impose a treatment to see how they respond.B.An experiment tries not to change behavior, an observational study does.C.An experiment deliberately imposes a treatment whereas an observational study measures the unintentional effects of the treatment as a result of the observation being done. QuestionBrian gathers data from his classmates about the computers they own:What are the individuals in this data set?AnswerA.The year purchasedB.Brian's classmatesC.The amount of memoryD.The type of operating systemQuestionA local newspaper in the State of Connecticut conducts a poll on whether the people of the state believe the "No Child Left Behind" law is effective. The newspaper contacts 1000 subscribers. The population of this poll is:AnswerA.Those who favor or disapprove of the "No Child Left Behind" lawB.People who live in the State of ConnecticutC.Those who are affected by "No Child Left Behind"D.The 1000 people surveyed QuestionThe Gallup Poll is an example of a:AnswerA.PopulationB.CensusC.ExperimentD.Sample SurveyCHAPTER 2QuestionThe BusinessWeek online poll is available at the BusinessWeek website. Visitors can simply click appropriate buttons to vote. In response to the question "Do you think Google is too powerful?" (March 27, 2007), 1336 said "Yes," 2051 said "No", and 335 said that they were not sure.Why do you think the poll may give unreliable information?AnswerA.Business Week uses convenience sampling.B.Online polls may not be reliable.C.Sample size is small. QuestionAs part of a project for a political science class, a student decided to conduct an online poll. The student asked the following question: “Do you think that illegal immigrants should be allowed to pay instate tuition, even though they are not legal citizens of that state?” Possible responses were Yes, No, and Unsure. Of those who responded, 81% said No, 19% said Yes, and 0% said Unsure. Which of the following statements correctly explains the result of the poll with respect to reliability and bias?AnswerA.The result of the poll is biased because it is based on voluntary response method.B.The result of the poll is not reliable because it is based on convenience sample method.C.The result of the poll can be considered reliable and unbiased. QuestionHighway planners decided to make a main street in West Lafayette, Indiana, a one-way street.? The Lafayette Journal and Courier took a one-day poll by inviting readers to call a telephone number to record their comments. The next day, the paper reported: “Journal and Courier readers overwhelmingly prefer two-way traffic flow in West Lafayette’s Village area to one-way streets. By nearly a 7-1 margin, callers to the newspaper’s Express Yourself opinion line on Wednesday complained about the one-way streets that have been in place since May. Of the 98 comments received, all but 14 said no to one-way.”What population do you think the newspaper wants information about?AnswerA.Highway plannersB.Residents of West Lafayette (and Lafayette)C.All readers of Lafayette Journal and Courier QuestionA national survey of TV network news viewers found that 48% said they would believe a phone-in poll of 300,000 persons rather than a random sample of 1000 persons. Of the viewers, 42% said they would believe the random sample poll. Which of the following statements correctly explains why the opinions of only 1000 randomly chosen respondents are a better guide to what all people think than the opinions of 300,000 callers?AnswerA.The 1000 randomly chosen respondents represent the population as a whole, whereas the 300,000 callers did not do so.B.The 1000 randomly chosen individuals were chosen as a personal choice of the TV network, whereas the 300,000 called voluntarily and do not represent the choice of the TV network.C.The 1000 randomly chosen respondents represent the intellectual population, whereas the 300,000 callers did not do so QuestionA university has 30,000 undergraduate and 10,000 graduate students. A survey of student opinion concerning health care benefits for domestic partners of students selects 300 of the 30,000 undergraduate students at random and then separately selects 100 of the 10,000 graduate students at random.? The 400 students chosen make up the sample.Which of the following statements correctly explains why this sampling method gives each student an equal chance to be chosen?AnswerEvery undergraduate student has a 75% chance of being selected and every graduate student has a 25% chance of being selected, which is proportional to the makeup of the student body.Any student has a 50% chance of being chosen, since the student is either selected or not.Any student, undergraduate or graduate, has a 1 in 100 chance of being selected. QuestionThe BusinessWeek online poll is available at the BusinessWeek website.? Visitors can simply click appropriate buttons to vote. In response to the question "Do you think Google is too powerful?" (March 27, 2007), 1336 said "Yes," 2051 said "No", and 335 said that they were not sure.Above the poll question, the following statement was mentioned: “Google’s accelerating lead in search and its moves into software and traditional advertising are sparking a backlash among rivals.”? How might this statement affect the polls?AnswerA.The statement would have increased the sample size.B.The statement would have made the poll biased.C.The statement would have made the poll reliable. QuestionA college wants to gather student opinion about parking for students on campus. It isn’t practical to contact all students.? Which of the following is an example of a good way to choose a sample?AnswerA.Selection of random 50 students and interviewing themB.A survey form published in the campus newspaperC.Interviewing students when they leave the parking at the campus QuestionIn 2005 the San Francisco Bay Times reported on a poll in New Zealand that found that New Zealanders opposed the nation’s new gay-inclusive civil-unions law by a 3-1 ratio. This poll was a call-in poll that cost $1 to participate in. The San Francisco Bay Times article also reported that a scientific polling organization found that New Zealanders favor the law by a margin of 56.4% to 39.3%. Which of the following statements is correct about the reliability of the polls?AnswerA.The polling result of neither call-in poll nor the scientific polling organization can be considered reliable as there is so much difference in the results of two polls.B.The scientific polling organization may not have produced the reliable result and therefore causing its results to differ so much with the result of the call-in poll.C.The call-in poll used the Voluntary Response method, so their poll results cannot be considered reliable. QuestionTo assess how its teaching assistants are performing, the statistics department at a large university randomly selects three of its teaching assistants each week and sends a faculty member to visit their classes. The current list of 20 teaching assistants is given below.?01. Bautista??? 06. Frazier??? 11. Miller??? 16. Walters02. Bolen??? 07. Kumar??? 12. Podboy??? 17. Wang03. Clottey??? 08. Lam??? ??? 13. Roy??? ??? 18. Weimer04. Counts??? 09. Lovesky??? 14. Schumacher??? 19. Yu05. Draper??? 10. Marin??? 15. Tower??? 20. ZhangThe department examines the first 13 two-digit groups in line 116 of Table A. Line 116 is:14459??????? 26056????????? 31424??????? 80371???????? 65103??????? 62253????????? 50490??? 61181.?The first 13 two-digits groups are: 14, 45, 92, 60, 56, 31, 42, 48, 03, 71, 65, 10, and 36.Which of the following teaching assistants would the sample consist of?AnswerA.Clottey, Marin, and SchumacherB.Draper, Marin, and SchumacherC.Bautista, Counts, and DraperD.Schumacher, Counts, and Draper QuestionChoosing at random is a "fair" way to decide who gets some scarce good, in the sense that everyone has the same chance to win. However, random choice isn’t always a good idea. At times we don’t want to treat everyone at the same because some people have a better claim. In which of the following situations, would you not prefer to choose at random?AnswerA.The basketball arena has 4000 student seats, and 7000 students want tickets.B.Young men chosen for army service, during the Vietnam War.C.The list of people waiting for liver transplants is larger than the number of livers available. QuestionHighway planners decided to make a main street in West Lafayette, Indiana, a one-way street.? The Lafayette Journal and Courier took a one-day poll by inviting readers to call a telephone number to record their comments. The next day, the paper reported: “Journal and Courier readers overwhelmingly prefer two-way traffic flow in West Lafayette’s Village area to one-way streets. By nearly a 7-1 margin, callers to the newspaper’s Express Yourself opinion line on Wednesday complained about the one-way streets that have been in place since May. Of the 98 comments received, all but 14 said no to one-way.” Which of the following statements is appropriate about the proportion of the population who favor one-way streets?AnswerA.The proportion of the population who favor one-way streets is probably equal to the proportion 14/98 in the sample.B.The proportion of the population who favor one-way streets is probably larger than the proportion 14/98 in the sample.C.The proportion of the population who favor one-way streets is probably smaller than the proportion 14/98 in the sample. QuestionThe BusinessWeek online poll is available at the BusinessWeek website.? Visitors can simply click appropriate buttons to vote. In response to the question "Do you think Google is too powerful?" (March 27, 2007), 1336 said "Yes," 2051 said "No", and 335 said that they were not sure.What was the sample size for this poll?AnswerA.335B.3722C.3136D.2051CHAPTER 3QuestionA November 2007 Gallup Poll of 1004 adults found that 572 are satisfied with the total cost they pay for their health care. The announced margin of error is ±3 percentage points. The announced confidence level is 95%.? Which of the statements is a correct and complete confidence statement in this scenario?AnswerA.We are 95% confident that p is between 54% and 60%.B.We are 95% confident that p is 57%.C.We are sure that p is between 54% and 60%. QuestionA management student is planning a project on student attitudes toward part-time work while attending college. She develops a questionnaire and plans to ask 25 randomly selected students to fill it out. Her faculty adviser approves the questionnaire but suggests that the sample size should be increased to at least 100 students.Which of the following statements correctly explains the advantage of the larger sample?AnswerA.A larger sample size will give less biased results.B.A larger sample size will give low bias and low variability.C.A larger sample size will give less variable results. QuestionA November 2007 Gallup Poll of 1004 adults found that 572 are satisfied with the total cost they pay for their health care. The announced margin of error is ±3 percentage points. The announced confidence level is 95%.? Which statement is true?AnswerA.The population parameter p is the proportion of the sample that is satisfied with the total cost they pay for their health care.B.The population parameter p is the proportion, of the total number of samples, which is within the limits of margin of error.C.The population parameter p is proportion of the population who is satisfied with the total cost they pay for their health care. QuestionA New York Times Poll on women’s issues interviewed 1025 women randomly selected from the United States, excluding Alaska and Hawaii. The poll found that 47% of the women said they do not get enough time for themselves. The poll announced a margin of error of ±3 percentage points for 95% confidence in its conclusions.Which of the following statements is the correct confidence statement, in relation to the scenario?AnswerA.We are 95% confident that between 44% and 50% of all women would say that they do not get enough time for themselves.B.We are sure that between 44% and 50% of all women would say that they do not get enough time for themselves.C.We are 95% confident that 47% of all women would say that they do not get enough time for themselves. QuestionA management student is planning a project on student attitudes toward part-time work while attending college. She develops a questionnaire and plans to ask 25 randomly selected students to fill it out. Her faculty adviser approves the questionnaire but suggests that the sample size should be increased to at least 100 students.Which of the following statements correctly identifies the relation between the margin of error for sample sizes of 100 and 25?AnswerA.The margin of error for a sample size of 100 will be approximately one-fourth of the margin of error for a sample size of 25.B.The margin of error for a sample size of 100 will be approximately double of the margin of error for a sample size of 25.C.The margin of error for a sample size of 100 will be approximately half of the margin of error for a sample size of 25. QuestionIn October 2007, the Gallup Poll asked a sample of 1010 adults, “Are you in favor of the death penalty for a person convicted of murder?” The proportion who said they were in favor was 69%. Gallup says that the margin of error for this poll is ±3 percentage points.Suppose you want a margin of error half as large as estimated by Gallup. How many people must you plan to interview?AnswerA.4040B.505C.2020 QuestionA New York Times Poll on women’s issues interviewed 1025 women randomly selected from the United States, excluding Alaska and Hawaii. The poll found that 47% of the women said they do not get enough time for themselves. The poll announced a margin of error of ±3 percentage points for 95% confidence in its conclusions.The confidence statement, in relation to the given scenario, is: “We are 95% confident that between 44% and 50% of all women would say that they do not get enough time for themselves.” Which of the following statements correctly explains the meaning of the term ‘95% confidence’, in the confidence statement?AnswerA.The interval 44% to 50% is based on a procedure that produces a margin of error (of ±3) 95% of the time.B.The interval 44% to 50% is based on a procedure that includes a sample representing 95% of population.C.The interval 44% to 50% is based on a procedure that captures the true population value 95% of the time. QuestionIn October 2007, the Gallup Poll asked a sample of 1010 adults, “Are you in favor of the death penalty for a person convicted of murder?” The proportion who said they were in favor was 69%.Gallup says that the margin of error for this poll is ±3 percentage points. Which of the following statements correctly explains the phrase “margin of error plus or minus 3 percentage points?”AnswerA.The true value is within 3 percentage points of the result obtained in this poll.B.The results are based on a method that is 95% of the time within 3 percentage points of the true value.C.The result of the poll is different from the true value by more than 3 percentage points. QuestionIn February 2004, USA Today conducted an online poll. Visitors to their Web site were asked the following question: “Should the U.S. pass a constitutional amendment banning gay marriage?” Visitors could vote by clicking a button. The result as of 3:30 pm on February 25 was that 68.61% voted “No” and 31.39% voted “Yes.” A total of 63,046 votes had been recorded. It was found that the margin of error for 95% confidence for a sample of this size is roughly equal to four-tenths of one percentage point.Which of the following statements correctly explains the result of the poll?AnswerA.The margin of error is 0.4%. Therefore, it can be said with 95% confidence that 68.61%, plus or minus 0.4%, of American adults are opposed to having the United States pass a constitutional amendment banning gay marriage.B.68.61% is the correct value of population parameter p, representing the proportion of American adults who are opposed to have the United States pass a constitutional amendment banning gay marriage.C.The result of the poll is based on a voluntary response sample. Therefore, it cannot be said that 68.61%, plus or minus 0.4%, of American adults are opposed to having the United States pass a constitutional amendment banning gay marriage. QuestionA New York Times Poll on women’s issues interviewed 1025 women randomly selected from the United States, excluding Alaska and Hawaii. The poll also interviewed 472 randomly selected men. In conclusions about women, the poll announced a margin of error of ±3 percentage points for 95% confidence.Which of the following statements is correct about the relation of margin of error for women and margin for error for men?AnswerA.The margin of error for men will be equal to the margin of error for women.B.The margin of error for men will be greater than margin of error for women.C.The margin of error for men will be smaller than the margin of error for women. QuestionA New York Times Poll on women’s issues interviewed 1025 women randomly selected from the United States, excluding Alaska and Hawaii. The poll found that 47% of the women said they do not get enough time for themselves. The poll announced a margin of error of ±3 percentage points for 95% confidence in its conclusions.Which of the following statements correctly explains why we can’t just say that 47% of all adult women do not get enough time for themselves?AnswerA.The result, that 47% women said they do not get enough time for themselves, is based on a sample that does not contain an equal proportion of the population from each state.B.The result, that 47% women said they do not get enough time for themselves, is based on a small sample size.C.The 47% of women who said they do not get enough time for themselves represents the proportion of the sample and not the proportion of the population.CHAPTER 4QuestionA survey of users of the Internet in 1995, when Internet use was much less common than now, found that males outnumbered females by nearly 2 to 1. This was a surprise because earlier surveys had put the ratio of men to women closer to 9 to 1. Later in the article we find this information: "Detailed surveys were sent to more than 13,000 organizations on the Internet; 1,468 usable responses were received. According to Mr. Quarterman, the margin of error is 2.8 percent, with a confidence level of 95 percent."Which of the following do you think is the source of error that has been disregarded?AnswerA.NonresponseB.Voluntary responseC.Undercoverage QuestionYou want to investigate the attitudes of students at your school toward the school’s policy on extra fees for lab courses. You have a grant that will pay the costs of contacting about 500 students.Which statement is true?AnswerA.A stratified sample can be created by using student majors as strata.B.A cluster sample is impossible in this situation.C.A cluster sample could be obtained by selecting ten students at random from EACH major. QuestionThe following question was asked in a sample survey: "In light of skyrocketing gasoline prices, we should consider opening up a very small amount of Alaskan wilderness for oil exploration as a way of reducing our dependence on foreign oil.? Do you agree or disagree?"????AnswerA.The question is slanted toward a desired response against the statement.B.The question is not slanted toward a desired response.C.The question is slanted toward a desired response in favor of the statement. QuestionYou want to investigate the attitudes of students at your school toward the school’s policy on extra fees for lab courses. You have a grant that will pay the costs of contacting about 500 students.Assuming that budget is not a constraint, which of the following would be the most appropriate method of contacting the students?????AnswerA.Mailed questionnairesB.Telephone interviewsC.Face-to-face interviews QuestionIn a sample survey, the following question was asked: "Which of the following best represents your opinion on gun control? 1. The government should take away our guns.2. We have the right to keep and bear arms.Identify the correct statement with reference to the survey question asked:AnswerA.The question is slanted toward a desired response in favor of the second statement.B.The question is slanted toward a desired response in favor of the first statement.C.The question is not slanted toward a desired response. QuestionWhen the Current Population Survey asked the adults in its sample of 50,000 households if they voted in the 2000 presidential election, 55% said they had. The margin of error was less than 1%. But, as a matter of fact, only 51% of the adult population voted in that election. Why do you think the CPS result missed by much more than the margin of error?AnswerA.The margin of error accounts for random sampling error only.B.The margin for error is not a suitable measure of sampling error.C.The margin of error is incorrectly calculated. QuestionAccording to a March 2007 USA Today/Gallup Poll, 43% of Americans identify themselves as baseball fans. That is low by recent standards, as an average of 49% of Americans have said they were fans of the sport since Gallup started tracking this measure in 1993. The high point came in 1998, when Sammy Sosa and Mark McGwire pursued (and ultimately surpassed) Roger Maris’s single-season home run record, at which time 56% of Americans considered themselves baseball fans. The Gallup press release says: "For results based on this sample, one can say with 95% confidence that the maximum error attributable to sampling and other random effects is ±3 percentage points."Which of the following sources of error do you think has been included in this reported margin of error? ????AnswerA.Voluntary responseB.UndercoverageC.NonresponseD.Random sampling error QuestionThe following example illustrates the idea of a systematic sample. Suppose that we must choose 4 rooms out of the 100 rooms in a dormitory. Because 100/4 = 25, we can think of the list of 100 rooms as four lists of 25 rooms each. Choose 1 of the first 25 rooms at random, using Table A. The sample will contain this room and the rooms 25, 50, and 75 places down the list from it. If 13 is chosen, for example, then the systematic random sample consists of the rooms numbered 13, 38, 63, and 88. Use Table A to choose a systematic random sample of 5 rooms from a list of 200. True or False:Like an Simple Random Sample (SRS), a systematic sample gives all individuals the same chance to be chosen. A systematic sample is, however, not an SRS.AnswerTrueFalse QuestionMatch the following sources of errors with appropriate categories.AnswerMatchQuestion ItemsAnswer ItemsA. - A.The subject lies about past drug use.A.Nonsampling error: a response errorB. - B.A typing error is made in recording the data.B.Nonsampling error: a processing errorC. - C.Data are gathered by asking people to go to a Web site and answer questions online.C.Sampling error: a voluntary response sampleCHAPTER 5QuestionWhat is the preferred treatment for breast cancer that is detected in its early stages? The most common treatment was once removal of the breast. It is now usual to remove only the tumor and nearby lymph nodes, followed by radiation. To study whether these treatments differ in their effectiveness, a medical team examines the records of 25 large hospitals and compares the survival times after surgery of all women who have had either treatment.Identify the explanatory and response variables in this study.AnswerA.Explanatory variable: Treatment method; Response variable: Survival timesB.Explanatory variable: Removal or non-removal of breast; Response variable: Women with breast cancerC.Explanatory variable: Survival times; Response variable: Treatment methodD.Explanatory variable: Women with breast cancer: Response variable: Removal or non-removal of breast QuestionWhat is the preferred treatment for breast cancer that is detected in its early stages? The most common treatment was once removal of the breast. It is now usual to remove only the tumor and nearby lymph nodes, followed by radiation. To study whether these treatments differ in their effectiveness, a medical team examines the records of 25 large hospitals and compares the survival times after surgery of all women who have had either treatment.True or false:The study is not an experiment because no treatment is actively imposed, and the patients or their doctors selected the treatment to be used.???AnswerTrueFalse QuestionCan aspirin help prevent heart attacks? The Physicians’ Health Study, a large medical experiment involving 22,000 male physicians, attempted to answer this question. One group of about 11,000 physicians took an aspirin every second day, while the rest took a placebo. After several years, the study found that subjects in the aspirin group had significantly fewer heart attacks than subjects in the placebo group.Match the terms used in experiments with their corresponding values in view of the given study.AnswerMatchQuestion ItemsAnswer ItemsA. - A.MedicationA.Explanatory variableB. - B.HealthB.Response variableC. - C.PhysiciansC.Subject QuestionA manufacturer of chisels is interested in determining how the angle at which the cutting edge is sharpened affects tool abrasion. To answer this question, engineers obtain 20 similar chisels. They sharpen five chisels at each of 22.5, 25, 27.5, and 30 degrees. Then, they measure the amount of abrasion (rated on a scale of 1 to 10, with 10 being the worst) after cutting several mortises (square holes) in 3/4-inch hard maple boards.Which of the following is the explanatory variable in the given study?AnswerA.Tool abrasionB.MortisesC.Sharpening of chiselsD.Angle of cutting edge QuestionA large study used records from Canada’s national health care system to compare the effectiveness of two ways to treat prostate disease. The two treatments are traditional surgery and a new method that does not require surgery. The records described many patients whose doctors had chosen one or the other method. The study found that patients treated by the new method were significantly more likely to die within eight years.You have 300 prostate patients who are willing to serve as subjects in an experiment to compare the two methods.Which of the following statements describes an appropriate design for this randomized comparative experiment?AnswerA.Assign the nonsurgical treatment to all patients and observe recovery. Then, assign the surgical treatment to the patients who do not recover and again observe recovery.B.Ask the patients to select the treatment method they want and divide them into two groups, one group with patients going for surgical treatment and the other group for nonsurgical treatment. Compare the recovery of patients in each group.C.Make two groups of 150 patients each by using random assignment. Give the surgical treatment to one group and the nonsurgical treatment to the other group. Observe the recovery of patients in each group. QuestionSome medical researchers suspect that the drug memantine improves the cognition of patients with moderate to severe Alzheimer’s disease. You have available 50 people with moderate to severe Alzheimer’s disease who are willing to serve as subjects.Consider the following design for the experiment, taking the placebo effect into account, will be to assign the placebo treatment to all 50 people. Next, measure the cognition of these people. Then, assign the memantine treatment to all and again check cognition.True or false:The given design is the most appropriate design for the experiment.AnswerTrueFalse QuestionDoes regular exercise reduce bone loss in postmenopausal women? Here are two ways to study this question. ???? A researcher finds 1000 postmenopausal women who exercise regularly. She matches each with a similar postmenopausal woman who does not exercise regularly, and she follows both groups for 5 years.???? Another researcher finds 2000 postmenopausal women who are willing to participate in a study. She assigns 1000 of the women to a regular program of supervised exercise. The other 1000 continue their usual habits. The researcher follows both groups for 5 years.Which of the following statements is correct with reference to the two studies?AnswerA.Only the second study will produce trustworthy data.B.Both of the studies will produce trustworthy data.C.Only the first study will produce trustworthy data.D.Neither of the studies will produce trustworthy data. QuestionA large study used records from Canada’s national health care system to compare the effectiveness of two ways to treat prostate disease. The two treatments are traditional surgery and a new method that does not require surgery. The records described many patients whose doctors had chosen one or the other method. The study found that patients treated by the new method were significantly more likely to die within eight years.Further study of the data showed that this conclusion was wrong. The extra deaths among patients treated with the new method could be explained by lurking variables.Identify a lurking variable that might be confounded with a doctor’s choice of surgical or nonsurgical treatment.AnswerA.Choice of the patient’s relativesB.Non-availability of surgical instrumentsC.Patient’s chance of survival QuestionCan aspirin help prevent heart attacks? The Physicians’ Health Study, a large medical experiment involving 22,000 male physicians, attempted to answer this question. One group of about 11,000 physicians took an aspirin every second day, while the rest took a placebo. After several years, the study found that subjects in the aspirin group had significantly fewer heart attacks than subjects in the placebo group.What is the meaning of the term “significantly” in “significantly fewer heart attacks”?AnswerA.It means “definitely occurred by chance if there was no difference between the aspirin and placebo groups.”B.It means “likely to have occurred by chance if there was no difference between the aspirin and placebo groups.”C.It means “definitely could not have occurred by chance if there was no difference between the aspirin and placebo groups.”D.It means “unlikely to have occurred by chance if there was no difference between the aspirin and placebo groups.” QuestionA manufacturer of chisels is interested in determining how the angle at which the cutting edge is sharpened affects tool abrasion. To answer this question, engineers obtain 20 similar chisels. They sharpen five chisels at each of 22.5, 25, 27.5, and 30 degrees. Then, they measure the amount of abrasion (rated on a scale of 1 to 10, with 10 being the worst) after cutting several mortises (square holes) in 3/4-inch hard maple boards.Identify the response variable in the given study.AnswerA.MortisesB.Amount of abrasionC.Cutting edge QuestionA study, mandated by Congress when it passed No Child Left Behind in 2002, evaluated 15 reading and math software products used by 9424 students in 132 schools across the country during the 2004–2005 school year. It is the largest study that has compared students who received the technology with those who did not, as measured by their scores on standardized tests. There were no statistically significant differences between students who used software and those who did not.Which of the following statements correctly describes the meaning of “no statistically significant differences”?AnswerA.There was no difference in the scores of students who used software and those who did not.B.There was a large difference in the scores of students who used software and those who did not. This difference could not have occurred by chance.C.There almost certainly was some difference in the scores of students who used software and those who did not. However, the difference was so small that it may have been due to chance alone. QuestionThe death rates of surgical patients differ for operations in which different anesthetics are used. An observational study found these death rates for four anesthetics:? Anesthetic:??? ??? Halothane??? ?????? Pentothal??? ??? Cyclopropane??? ????????? EtherDeath rate:??? ?????? 1.7%??? ??????????????? 1.7%??? ???????????????? 3.4%??? ??????????????? 1.9%This is not good evidence that cyclopropane is more dangerous than the other anesthetics.Identify a lurking variable that may be confounded with the choice of anesthetic in surgery and that could explain the different death rates.AnswerA.Financial background of the patientB.Types of surgical instrumentsC.Physical condition of the patient ................
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