Stats Test
A news release for a diet product company reports: "There's good news for the 65 million Americans currently on a diet." Its own study showed that people who lose weight can keep it off. The sample was 20 graduates of the company's program who endorsed the program in commercials. The results of the sample are probably: A)biased, overstating the effectiveness of the diet. B)biased, understating the effectiveness of the diet. C)unbiased, because the people in the sample are nationally recognized individuals. D)unbiased, but they could be more accurate if a larger sample size was used.
A
A researcher finds 1000 mildly overweight women who exercise regularly, have not had a heart attack, and are willing to participate in the study. She randomly assigns 500 of the women to take an appetite suppressant. The other 500 women are given a placebo. Both groups are followed for five years, and the amount of weight lost after this time is recorded. The response variable in this experiment is: A)the amount of weight lost. B)the proportion of women in each group that stayed in the study. C)whether the women exercised. D)the age of the women.
A
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. A random sample allows which tool to be used for trustworthy inference? A)the laws of probability B)the laws of correct surveys C)the laws of generality D)All of the answer options are correct.
A
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist used an introductory sociology class to carry out the survey and asked only the freshmen to answer the questions. The sample is called: A)a convenience sample. B)a volunteer sample. C)a random sample. D)a targeted sample.
A
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. Which of the following strategies will provide a simple random sample? A)Contacting the registrar and obtaining a list of all freshmen, from which a random sample will then be selected. B)Using the enrollment list of the introductory class and selecting all the freshmen. C)Using the class list of the introductory class and randomly selecting a fraction of the students enrolled. D)Using all the students in the class because, after all, they resemble typical students at the university.
A
A student asks each person in one of his classes how many hours, on average, they spend studying each week. This is an example of: A)convenience sampling. B)a double-blind experiment. C)a simple random sample. D)voluntary response sampling.
A
A study attempts to compare two sunscreens. Each of 50 subjects with varying skin complexions will use both sunscreens-Screen A on one side of the body and Screen B on the other side. For each subject, a coin is tossed to determine which side receives Screen A and which receives Screen B. Researchers measure the amount of ultraviolet light exposure over both treated areas for each subject. This is an example of: A)a matched pairs experiment. B)a double-blind observational study. C)a stratified analysis. D)the placebo effect.
A
A study is conducted to investigate the effects of a new exercise program on lameness in race horses. A group of horses at a local race track is selected for the study. The horses are randomly assigned to two groups. Group 1 horses will train according to the new program for one month, rest for two weeks, and then train according to the old program for one month. Group 2 horses will have the order of the old and new programs reversed. Here, each horse serves as its own control. The two groups are necessary to avoid: A)a carryover effect, since the order of treatment may influence the subject's response. B)a placebo effect. C)a double-blind effect. D)a confounded effect
A
A veterinarian interested in studying the causes of enteroliths in horses suspects that a diet high in alfalfa may be a cause. The veterinarian decides to use the following design: identify 30 horses at high risk for enteroliths, and divide them into 10 groups of 3 horses. Some groups consist of horses in barn stalls, some groups consist of horses in outdoor paddocks, and some groups consist of horses in pastures. Within each group, one horse is randomly assigned to an alfalfa diet, one is assigned to a grass hay diet, and one horse is fed oat hay. When a horse is in a pasture, all the other horses in that pasture will also receive the diet of the study horse. Therefore, only one horse could be selected from a given pasture. The study is: A)a randomized block design. B)a matched pairs design. C)a completely randomized design. D)a comparative observational design.
A
A veterinarian interested in studying the causes of enteroliths in horses suspects that a diet high in alfalfa may be a cause. The veterinarian decides to use the following design: identify 30 horses at high risk for enteroliths, and divide them into 10 groups of 3 horses. Some groups consist of horses in barn stalls, some groups consist of horses in outdoor paddocks, and some groups consist of horses in pastures. Within each group, one horse is randomly assigned to an alfalfa diet, one is assigned to a grass hay diet, and one horse is fed oat hay. When a horse is in a pasture, all the other horses in that pasture will also receive the diet of the study horse. Therefore, only one horse could be selected from a given pasture. This study has: A)one factor and three treatments. B)one treatment and three factors. C)three treatments and three factors. D)one factor and one treatment.
A
Advice columnist Ann Landers once asked her readers with children to answer the following question: "If you had it to do over again, would you have children?" Readers were invited to send a response to this question by mail. Of the approximately 10,000 responses Landers received, approximately 70% said "no." The sample is: A)the approximately 10,000 readers who wrote in. B)the approximately 70% of women who answered "no." C)the respondents who regretted having children. D)all readers.
A
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. After consultation with a statistician, the educator decides to randomly allocate students to either a group that will sleep for 8 hours the night before class or 6 hours. The educator does not know which group a student belongs to when she or he comes to class. The educator, after talking to some students and before the experiment, decides that the number of classes students have on the same day before calculus could potentially confound the study and wishes to make an adjustment. The design that allows for such an adjustment is called: A)a randomized block design. B)a placebo controlled completely randomized design. C)a double-blinded design. D)a matched block design.
A
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. Before the start of the class, each student is asked about the number of hours slept the previous night. Each student's eye movement is then tracked throughout the lecture. The amount of time is recorded whenever the student is not focused on either the instructor or taking notes. This is an example of: A)an observational study. B)a sample survey. C)a randomized experiment. D)a matched pairs study.
A
An insurance underwriter wonders whether sports cars "cause" people to drive too fast or whether those with a propensity for speeding are drawn to sports cars. She secures some research funds and recruits 100 car buyers to her study. She randomly assigns 25 drivers to each of four groups: 1) sports car white, 2) sports car red, 3) sedan white, or 4) sedan red. The primary research questions are: 1) Do sports cars make people drive faster? and 2) Does color make a difference? This study has: A)four treatments. B)two treatments. C)four treatments and a placebo. D)two treatments and a placebo.
A
In a study of human development, investigators showed two different types of movies to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. One type of movie was shown at 8 A.M. (right after the children had breakfast) and the other type of movie was shown at 11 A.M. (right before the children were to have lunch). It was found that more crackers were eaten during the movie shown at 11 A.M. than during the movie shown at 8 A.M. The investigators concluded that the different types of movies had different effects on appetite. The response variable in this experiment is: A)the number of crackers eaten. B)the different types of movies. C)the time each movie was shown. D)the bowls.
A
In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three treatment groups: (1) gastric bypass surgery, (2) participation in a diet and exercise program, or (3) both gastric bypass surgery and participation in a diet and exercise program. Researchers observed the amount of weight lost five years after the study began. This study uses the principles of: A)randomization. B)confounding. C)blocking. D)All of the answer options are correct.
A
Randomly assigning all subjects to treatment groups is called: A)a completely randomized design. B)a randomized complete block design. C)a randomized comparative experiment. D)None of the answer options is correct.
A
The magazine High Times has a website that once asked visitors whether recreational marijuana use should be legal. This is an example of: A)voluntary response sampling. B)a survey with little bias, because a large simple random sample was used. C)a survey with little bias, because someone who responded would know his or her opinion. D)All of the answer options are correct.
A
To investigate whether women are more likely than men to prefer Democratic candidates, a political scientist selects a large sample of registered voters, both men and women. She asks every voter whether they voted for the Republican or the Democratic candidate in the last election. This is: A)an observational study. B)a multistage sample. C)a double-blind experiment. D)a block design.
A
A 1992 Roper poll found that 22% of Americans say that the Holocaust may not have happened. The actual question asked in the poll was "Does it seem possible or impossible to you that the Nazi extermination of the Jews never happened?" and 22% responded "possible." The results of this poll cannot be trusted because: A)undercoverage is present-obviously, those people who did not survive the Holocaust could not be in the poll. B)the question is worded in a confusing manner. C)we do not know who conducted the poll or who paid for the results. D)nonresponse is present-many people will refuse to participate, and those who do will be biased in their opinions.
B
A group of veterinarians at a major veterinary hospital was interested in investigating a possible link between enteroliths (stones that form in the colon of horses) and diet. They decided to conduct a survey of the feeding practices for horses in the hospital's state. They created a survey questionnaire and decided to administer it to the owners of every fifth horse being treated at the hospital. The population of interest is: A)all horses brought to the clinic. B)all horses in the state. C)all horses that are diagnosed with enteroliths. D)None of the answer options is correct.
B
A political party sends a mail survey to 1500 randomly selected registered voters in a community. The survey asks respondents to give an opinion about the job performance of the current president. Of the 1500 surveys sent out, 480 are returned, and of these, only 120 show that the respondent is satisfied with the president's job performance. The sample is: A)the 1500 randomly selected voters who received the questionnaire. B)the 480 surveys returned. C)the 120 voters surveyed who are satisfied with the president's job performance. D)the voters in the president's district.
B
A public opinion poll in Ohio was set up to determine whether registered voters in the state approved of a measure to ban smoking in all public areas. The researchers selected a simple random sample of 50 registered voters from each county in the state and asked whether the voters approved or disapproved of the measure. This is an example of: A)a systematic county sample. B)a stratified sample. C)a multistage sample. D)a simple random sample.
B
A researcher studying the effect of price cuts on consumers' expectations makes up two different histories of the store price of a hypothetical brand of laundry detergent for the past year. Eight students in a business class view one or the other price history on a computer. Some students see a steady price, whereas others see regular sales that temporarily cut the price. Students are asked the price they would expect to pay. The experimental units are: A)all business students at the college. B)the eight business students who participated. C)the business students who were in the fluctuating price group. D)the price the students would expect to pay.
B
A small math department has six faculty members and 30 students. The department can send six people to a national convention, and it would like to send four students and two faculty members. Of the 30 students, four are selected randomly. Two faculty members are randomly selected from the six. This is an example of: A)simple random sampling. B)stratified random sampling. C)voluntary response sampling. D)a census.
B
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist decides to use his introductory sociology class to conduct the survey. If the survey is not representative of the freshmen at the university, the conclusions from the study are likely to be: A)on target. B)biased. C)overefficient. D)None of the answer options is correct.
B
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist, who knows about proper sampling, selects which type of a sample? A)a volunteer sample B)a random sample C)a two-step sample D)a hierarchical sample
B
A student organization wanted to study voting preferences in its student body during the 2012 presidential election. They selected 120 students at random from each class, freshmen through seniors. The sampling technique used is: A)simple random sampling. B)stratified random sampling. C)volunteer sampling. D)multistage sampling.
B
A study is done to assess the effects of a new medication on the resting heart rate of dogs. Two breeds will be used in the study because of the availability of experimental subjects, even though the researcher is not interested in the differences in the medication's effectiveness between breeds. What type of experimental design should be used? A)no blinding; no blocking B)no blinding; blocking on dog breed C)double blind; no blocking D)double blind; blocking on dog breed
B
A veterinarian interested in studying the causes of enteroliths in horses suspects that a diet high in alfalfa may be a cause. The veterinarian decides to use the following design: identify 30 horses at high risk for enteroliths, and divide them into 10 groups of 3 horses. Some groups consist of horses in barn stalls, some groups consist of horses in outdoor paddocks, and some groups consist of horses in pastures. Within each group, one horse is randomly assigned to an alfalfa diet, one is assigned to a grass hay diet, and one horse is fed oat hay. When a horse is in a pasture, all the other horses in that pasture will also receive the diet of the study horse. Therefore, only one horse could be selected from a given pasture. The blocking is done: A)to reduce the potentially confounding effect of comparing more than two treatments. B)to reduce the potentially confounding effect that the type of housing may have. C)to increase the treatment effects. D)All of the answer options are correct.
B
A veterinarian is interested in studying the causes of enteroliths (stones that form in the gut of horses). An observational study comparing the diet of horses admitted to the veterinary hospital with enteroliths and the diet of horses admitted for other reasons does not allow causal conclusions to be drawn because: A)an observational study can only establish correlations, unless the investigator is double blinded. B)associations in observational studies can be confounded by lurking variables. C)the study does not match horses. D)All of the answer options are correct.
B
Advice columnist Ann Landers once asked her readers with children to answer the following question: "If you had it to do over again, would you have children?" Readers were invited to send a response to this question by mail. Of the approximately 10,000 responses Landers received, approximately 70% said "no." The population of interest is: A)the more than 10,000 people who responded. B)all readers who are parents. C)the readers with children who regret having children. D)the children who are unwanted.
B
Advice columnist Ann Landers once asked her readers with children to answer the following question: "If you had it to do over again, would you have children?" Readers were invited to send a response to this question by mail. Of the approximately 10,000 responses Landers received, approximately 70% said "no." The sample: A)is probably representative of all parents. B)is probably not representative of all parents, because people who feel very strongly about this issue are more likely to respond than people who do not. C)has little bias, because more than 10,000 people responded, yielding a very large sample. D)is probably not representative, because more than 10,000 people responded.
B
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. After consultation with a statistician, the educator decides to randomly allocate students to either a group that will sleep for 8 hours the night before class or 6 hours. The educator does not know which group a student belongs to when she or he comes to class. The study subjects are: A)the groups assigned to sleeping either 6 or 8 hours. B)the students participating in the experiment. C)the students who do not fall asleep in class. D)the students who are enrolled in any of the calculus classes.
B
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. Before the start of the class, each student is asked about the number of hours slept the previous night. Each student's eye movement is then tracked throughout the lecture. The amount of time is recorded whenever the student is not focused on either the instructor or taking notes. The class is held at 11 A.M. and the instructor also asks questions about prior classes that day. The response variable is: A)the number of hours slept the night before. B)the amount of time not focused. C)the time of day the class is given. D)the number of prior classes that day.
B
An insurance underwriter wonders whether sports cars "cause" people to drive too fast or whether those with a propensity for speeding are drawn to sports cars. She secures some research funds and recruits 100 car buyers to her study. She randomly assigns 25 drivers to each of four groups: 1) sports car white, 2) sports car red, 3) sedan white, and 4) sedan red. The primary research questions are: 1) Do sports cars make people drive faster? and 2) Does color make a difference? The result shows that people driving red cars drive faster than those driving white cars. There is no statistically significant difference by type. This conclusion is: A)wrong, because the stated purpose was to study type, not color. B)valid, because this was a randomized study and drivers were randomized on color and type. C)wrong, because you cannot study two different things, like type and color, at once. D)valid, because sports cars obviously make people drive fast.
B
Apparently, according to some studies, men who drive expensive sports cars have lower blood pressure and fewer cardiovascular health problems. We can't conclude that driving expensive sports cars lowers blood pressure or improves cardiovascular health because the studies described are clearly: A)experiments. B)observational studies, not experiments-lurking variables may explain the association. C)paired data experiments. D)stratified experiments.
B
Each month, the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don't return the form. In one month, responses were obtained from 240,000 of the households contacted. The sample is: A)the 250,000 households initially contacted. B)the 240,000 households that responded. C)the 10,000 households that did not respond. D)all U.S. households.
B
In a study of human development, investigators showed two different types of movies to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. One type of movie was shown at 8 A.M. (right after the children had breakfast) and the other type of movie was shown at 11 A.M. (right before the children were to have lunch). It was found that more crackers were eaten during the movie shown at 11 A.M. than during the movie shown at 8 A.M. The investigators concluded that the different types of movies had different effects on appetite. The treatment in this experiment is: A)the number of crackers eaten. B)the different kinds of movies. C)the time each movie was shown. D)the bowls.
B
In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three treatment groups: (1) gastric bypass surgery, (2) participation in a diet and exercise program, or (3) both gastric bypass surgery and participation in a diet and exercise program. Researchers observed the amount of weight lost five years after the study began. The response is: A)the kind of program to which a subject was assigned. B)the amount of weight lost five years after the study began. C)gastric bypass surgery. D)random assignment.
B
In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three treatment groups: (1) gastric bypass surgery, (2) participation in a diet and exercise program, or (3) both gastric bypass surgery and participation in a diet and exercise program. Researchers observed the amount of weight lost five years after the study began. This study has: A)four factors. B)three treatments. C)two treatments. D)None of the answer options is correct.
B
Researchers have noted that children who learn to play a musical instrument through taking lessons have higher average SAT scores, higher average GPAs, and higher average class ranks. The various measures of academic success described are examples of: A)explanatory variables. B)response variables. C)confounding variables. D)None of the answer options is correct.
B
Researchers have noted that children who learn to play a musical instrument through taking lessons have higher average SAT scores, higher average GPAs, and higher average class ranks. This is an example of: A)an experiment. B)an observational study. C)the establishing of a causal relationship through correlation. D)a block design, with music and no-music groups as blocks.
B
Some researchers have noted that adolescents who spend a lot of time playing video or computer games are at greater risk for depression and violence. This is an example of: A)a valid conclusion, because more time yields more aggression is a positive association. B)an observational study with lurking variables that may explain the association. C)a single-blind experiment, because the subjects knew they were playing games. D)a paired data experiment, because we are studying both aggression and game playing.
B
Veterinarians often use nonsteroidal anti-inflammatory drugs (NSAIDs) to treat lameness in horses. A group of veterinary researchers wanted to find out how widespread the practice is in the United States. They obtained a list of all veterinarians treating large animals, including horses. They sent questionnaires to all the veterinarians on the list. Such a survey is called a census. The response rate was 40%. Which of the following statements is correct? A)The sample consisted of all veterinarians on the list and, therefore, equaled the target population. B)The sample consisted of all veterinarians who returned the questionnaire. C)The sample consisted of all veterinarians who treat horses with NSAIDs. D)None of the answer options is correct.
B
A group of veterinarians at a major veterinary hospital was interested in investigating a possible link between enteroliths (stones that form in the colon of horses) and diet. They decided to conduct a survey of the feeding practices for horses in the hospital's state. They created a survey questionnaire and decided to administer it to the owners of every fifth horse being treated at the hospital. The sample is: A)a volunteer sample. B)a simple random sample. C)a convenience sample. D)a stratified random sample.
C
A nutritionist has designed an intervention to motivate parents of preschool children to provide more fruits and vegetables to their children. To study the effectiveness of this intervention, the nutritionist will conduct an experiment in which half of the selected study participants will receive the intervention and the others will not. Study subjects will be recruited from families with children who receive medical care for their children through the university health center. One factor that must be accounted for is whether the family receives aid through the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), which provides funds for fruits and vegetables to the mothers. Which of the following experiments should the nutritionist use? A)a completely randomized design B)a matched design where children are matched on age and gender, and the WIC child does not get the intervention C)a randomized matched pairs design where parents are matched on age, gender, and WIC program participation D)a matched pairs observational study
C
A nutritionist has designed an intervention to motivate parents of preschool children to provide more fruits and vegetables to their children. To study the effectiveness of this intervention, the nutritionist will conduct an experiment in which half of the selected study participants will receive the intervention and the others will not. Study subjects will be recruited from families with children who receive medical care for their children through the university health center. The nutritionist will compare the amount of fruit consumed per day by the children in families who received the intervention and by those who did not. Which of the following is true? A)The amount of fruit consumed is the treatment. B)The amount of fruit consumed is the factor. C)The amount of fruit consumed is the response. D)The amount consumed is the carryover effect from before and after the intervention.
C
A researcher finds 1000 mildly overweight women who exercise regularly, have not had a heart attack, and are willing to participate in the study. She randomly assigns 500 of the women to take an appetite suppressant. The other 500 women are given a placebo. Both groups are followed for five years, and the amount of weight lost after this time is recorded. The factor in the experiment is: A)the weight lost by women in the study. B)the use of a control group taking a placebo. C)the treatment taken by women in the study-appetite suppressant or placebo. D)the length of the study.
C
A researcher studying the effect of price cuts on consumers' expectations makes up two different histories of the store price of a hypothetical brand of laundry detergent for the past year. Eight students in a business class view one or the other price history on a computer. Some students see a steady price, whereas others see regular sales that temporarily cut the price. Students are asked the price they would expect to pay. This is an example of: A)a matched pairs experiment. B)a two-factor design. C)a randomized comparative experiment. D)a randomized observational study.
C
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist used an introductory sociology class to carry out the survey. The population of interest is: A)the students at the university. B)the students in the sociology class. C)the freshmen at the university. D)the freshmen in the sociology class.
C
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist used an introductory sociology class to carry out the survey. The sociologist has learned from previous studies that females and males often behave differently regarding study and sleep patterns. She decides that she needs to ensure adequate numbers of females and males. She should take: A)a multi-stage sample. B)two convenience samples, one of females and one of males. C)a stratified random sample. D)a multi-group sample.
C
A veterinarian interested in studying the causes of enteroliths (stones that form in the gut of horses) decided to compare the diets of horses with enteroliths and horses without that were admitted to the veterinary hospital. This study is an example of: A)an experimental study. B)a survey. C)an observational study. D)None of the answer options is correct.
C
A veterinarian is interested in studying the causes of enteroliths (stones that form in the gut of horses). In order to establish a causal relationship between diet and enteroliths, the veterinarian needs to: A)use a double-blind observational study. B)use a nonrandomized experimental design in which the examining veterinarian is blinded to the diet the horse is fed. C)use a comparative randomized experiment. D)use a survey questionnaire that is to be administered to all horse owners entering the veterinary hospital.
C
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. Each student enrolled in the class is randomly assigned to either sleeping 6 or 8 hours the night before. Each student's eye movement is then tracked throughout the lecture. The amount of time is recorded whenever the student is not focused on either the instructor or taking notes. This study has: A)one factor and one treatment. B)two factors and one treatment. C)one factor and two treatments. D)two factors and two treatments.
C
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. The educator has contacted a statistician to help plan a proper study for the assessment of cause and effect. The type of study required is called: A)a replicated observational study. B)a quasi-experiment. C)a completely randomized design. D)a blocked study.
C
An insurance underwriter wonders whether sports cars "cause" people to drive too fast or whether those with a propensity for speeding are drawn to sports cars. She secures some research funds and recruits 100 car buyers to her study. She randomly assigns 25 drivers to each of four groups: 1) sports car white, 2) sports car red, 3) sedan white, and 4) sedan red. The primary research questions are: 1) Do sports cars make people drive faster? and 2) Does color make a difference? The underwriter finds that drivers of red sports cars are the fastest, followed by drivers of red sedans. Her conclusion is that: A)driving a sports car makes people drive fast. B)driving a red sports car makes people drive fast. C)driving a red car makes people drive fast. D)All of the answer options are correct.
C
An insurance underwriter wonders whether sports cars "cause" people to drive too fast or whether those with a propensity for speeding are drawn to sports cars. She secures some research funds and recruits 100 car buyers to her study. She randomly assigns 25 drivers to each of four groups: 1) sports car white, 2) sports car red, 3) sedan white, and 4) sedan red. The primary research questions are: 1) Do sports cars make people drive faster? and 2) Does color make a difference? The underwriter worries that gender affects driving behavior and thinks it may actually be a confounder. She decides to randomize males and females separately. This is a: A)randomized study with one factor and two blocking variables. B)randomized study with two factors and one blocking variable. C)randomized study with three factors. D)None of the answer options is correct.
C
At a large university, a simple random sample of five female professors is selected, and a simple random sample of 10 male professors is selected. The two samples are combined to give an overall sample of 15 professors. The overall sample is: A)a simple random sample. B)biased due to imbalance. C)a stratified sample. D)All of the answer options are correct.
C
Each month, the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don't return the form. In one month, responses were obtained from 240,000 of the households contacted. A household that does not return the form and cannot be contacted by telephone is an example of: A)simple random sampling. B)undercoverage. C)nonresponse. D)volunteer bias.
C
One hundred sixty people who suffer from painful diabetic neuropathy have volunteered to participate in a study. Eighty are selected at random and are given the drug gabapentin, which (although originally intended to prevent epileptic seizures) has properties that may make it useful to alleviate neuropathy. The remaining participants are given a placebo. A neurologist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of the symptoms. Does the use of volunteers make this study invalid? A)Yes, because of volunteer bias. B)Yes, because there is no way to determine the effect of the drug on people that do not have symptoms of neuropathy. C)No, because the subjects are randomly assigned to treatment groups. D)No, because blocking was used.
C
One hundred sixty people who suffer from painful diabetic neuropathy have volunteered to participate in a study. Eighty are selected at random and are given the drug gabapentin, which (although originally intended to prevent epileptic seizures) has properties that may make it useful to alleviate neuropathy. The remaining participants are given a placebo. A neurologist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of the symptoms. Suppose the volunteers were first divided into men and women, and then half of the men were randomly assigned to the new drug and half of the women were assigned to the new drug. The remaining volunteers received the placebo. This would be an example of: A)replication. B)confounding-the effects of gender will be mixed up with the effects of the drug. C)a block design. D)a matched pairs design.
C
One hundred sixty people who suffer from painful diabetic neuropathy have volunteered to participate in a study. Eighty are selected at random and are given the drug gabapentin, which (although originally intended to prevent epileptic seizures) has properties that may make it useful to alleviate neuropathy. The remaining participants are given a placebo. A neurologist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of the symptoms. This study would be double-blind if: A)neither drug had any identifying marks on it. B)neither the volunteers nor the neurologist were allowed to see each other during the session in which the neurologist evaluated the severity of the symptoms. C)neither the volunteers nor the neurologist knew which subjects had received the drug and which had received the placebo. D)All of the answer options are correct.
C
Sickle-cell disease is a painful disorder of the red blood cells that, in the United States, affects mostly African Americans. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by the National Institutes of Health gave the drug to 150 sickle-cell sufferers and a placebo to another 150. Neither doctors nor patients were told who received the drug. The number of episodes of pain reported by each subject was recorded. This is an example of: A)an observational study. B)an experiment, but not a double-blind experiment. C)a double-blind experiment. D)a paired data experiment.
C
Surveys, if not done correctly, can lead to seriously biased samples. Which of the following is not a bias due to the sampling plan? A)bias due to selecting a volunteer sample B)bias due to selecting a convenience sample C)bias due to nonresponse D)bias due to selecting a stratified random sample
C
The Excite Poll is an online poll at poll.excite.com. You click on an answer to become part of the sample. One poll question was "Do you prefer watching first-run movies at a movie theater or waiting until they are available on home video or pay-per-view?" A total of 8896 people responded, with 1118 saying they preferred theaters. From this survey, you should conclude that: A)Americans prefer watching movies at home. B)a larger sample is necessary. C)the poll uses voluntary response, so the results tell us little about the population of all adults. D)movie theaters should lower their prices.
C
The purpose of blocking is: A)to arrange experimental units according to similarity. B)to ensure that the results from an experiment are accurate. C)to control the effects of an outside variable that is not of interest to the researchers. D)All of the answer options are correct.
C
To assess the opinion of students at The Ohio State University about campus safety, a reporter for the student newspaper interviews 15 students that she meets walking on the campus late at night who are willing to give their opinion. The method of sampling used is: A)simple random sampling. B)a Gallup Poll. C)voluntary response. D)a census.
C
To assess the opinion of students at The Ohio State University about campus safety, a reporter for the student newspaper interviews 15 students that she meets walking on the campus late at night who are willing to give their opinion. The sample is: A)all those students walking on campus late at night. B)all students at universities with safety issues. C)the 15 students interviewed. D)all students approached by the reporter.
C
To select a sample of undergraduate students in the United States, I first 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: A)simple random sampling. B)stratified random sampling. C)multistage sampling. D)convenience sampling.
C
Veterinarians often use nonsteroidal anti-inflammatory drugs to treat lameness in horses. A group of veterinary researchers wanted to find out how widespread the practice is in the United States. They obtained a list of all veterinarians treating large animals, including horses. They sent questionnaires to all the veterinarians on the list. Such a survey is called a census. The response rate was 40%. What is the population of interest? A)all veterinarians B)all veterinarians treating large animals C)all veterinarians in the United States treating large animals, including horses D)All of the answer options are correct.
C
35/50 Quiz 9: Producing Data- Experiments Statistics 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 used 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: A)display a high degree of statistical significance, and so the treatment will work in humans with nearly 100% certainty. B)are convincing, assuming the results have been replicated in a large number of mice. C)are convincing, assuming that proper randomization and control were used. D)suffer from lack of realism.
D
A group of veterinarians at a major veterinary hospital was interested in investigating a possible link between enteroliths (stones that form in the colon of horses) and diet. They decided to conduct a survey of the feeding practices for horses admitted to the veterinary hospital. To obtain a simple random sample, they used a computer to generate 4-digit ID numbers for all horses. They used random digit tables to select the horses. Which of the following is a step in selecting a random sample by this procedure? A)Pick a random starting point in the table and read 4 digits. B)Read 4 digits across a line, and if the 4 digits correspond to a horse ID, select the animal. C)Discard any sequence that does not correspond to a horse ID, and move to the next 4 digits. D)All of the answer options are correct.
D
A placebo is an important element of many clinical trials because: A)it serves as a control for the experiment. B)it allows the researcher to adjust for the psychological effects of receiving medical attention. C)the use of the placebo can help avoid confounding. D)All of the answer options are correct.
D
A political party sends a mail survey to 1500 randomly selected registered voters in a community. The survey asks respondents to give an opinion about the job performance of the current president. Of the 1500 surveys sent out, 480 are returned, and of these, only 120 show that the respondent is satisfied with the president's job performance. The population is: A)the 1500 registered voters in the community selected to receive the survey. B)the 480 respondents who answered the survey. C)the 120 respondents satisfied with the president's job performance. D)all registered voters in the community.
D
A political party sends a mail survey to 1500 randomly selected registered voters in a community. The survey asks respondents to give an opinion about the job performance of the current president. Of the 1500 surveys sent out, 480 are returned, and of these, only 120 show that the respondent is satisfied with the president's job performance. This is an example of: A)a survey with little bias, because an individual will know for certain whether he or she approves of the president's job performance. B)a survey with little bias, because 1500 voters represent an important part of the president's district. C)a survey with no bias. D)None of the answer options is correct.
D
A properly designed survey should have which of the following? A)a random sample B)a carefully defined objective C)a clearly defined population of interest D)All of the answer options are correct.
D
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. Students will often overstate the number of hours studied, because they do not want to admit to not studying enough. This type of distortion is called: A)false answer. B)non-response bias. C)undercoverage bias. D)response bias.
D
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist used an introductory sociology class to carry out the survey, instructing the students to participate only if they were freshmen. The sample consists of: A)the students enrolled in the class. B)the students who were in class for the survey and answered the survey questions. C)the freshmen at the university. D)the freshmen in the class who answered the survey questions.
D
A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist, who would like a simple random sample but finds it too time consuming to obtain such a sample, decides to use all students enrolled in his own class. This type of sample: A)is a convenience sample. B)likely results in undercoverage of certain types of freshmen. C)could lead to biased conclusions. D)All of the answer options are correct.
D
A veterinarian interested in studying the causes of enteroliths in horses suspects that a diet high in alfalfa may be a cause. The veterinarian decides to use the following design: identify 30 horses at high risk for enteroliths, and divide them into 10 groups of 3 horses. Some groups consist of horses in barn stalls, some groups consist of horses in outdoor paddocks, and some groups consist of horses in pastures. Within each group, one horse is randomly assigned to an alfalfa diet, one is assigned to a grass hay diet, and one horse is fed oat hay. When a horse is in a pasture, all the other horses in that pasture will also receive the diet of the study horse. Therefore, only one horse can be selected from a given pasture. After one year, the horses are given radiographs to determine if enteroliths are present in the gut. The response is: A)the diet a horse is given. B)the amount of feed a horse is given. C)the number of enteroliths. D)the presence or absence of enteroliths.
D
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. After consultation with a statistician, the educator decides to randomly allocate students to either a group that will sleep for 8 hours the night before class or 6 hours. The educator does not know which group a student belongs to when she or he comes to class. This study is: A)double blinded, because the educator does not know who belongs to the 6- or 8-hour group. B)double blinded, because the students have been told not to inform the educator about the treatment group they belong to. C)a placebo controlled study, because 8 hours is normal sleeping time. D)a single blinded randomized study, because the educator does not know the treatment groups students belong to but the students know.
D
An educator wishes to study the effects of sleep deprivation on the ability to concentrate. He decides to study the students in a calculus class. Before the start of the class, each student is asked about the number of hours slept the previous night. Each student's eye movement is then tracked throughout the lecture. The amount of time is recorded whenever the student is not focused on either the instructor or taking notes. The class is offered at 11 A.M. A potential confounder is given by the number of classes a student has prior to calculus because: A)the larger the number of classes earlier in the day, the earlier the student has to get up and therefore sleeps less. B)the larger the number of classes earlier in the day, the more a student has to prepare and likely stays up late. C)many classes earlier in the day will leave a student tired just from having to stay focused for several hours. D)All of the answer options are correct
D
At a local health club, a researcher samples 75 people whose primary exercise is cardiovascular and 75 people whose primary exercise is strength training. The researcher's objective is to assess the affect of type of exercise on cholesterol. Each subject reported to a clinic to have his or her cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of the subject's type of exercise. This approach is: A)an observational study. B)an experiment, but not a double-blind experiment. C)a double-blind experiment. D)fundamentally flawed, because only a well-designed experiment with randomized assignment to treatments can be used to determine a cause-and-effect relationship.
D
During the 1936 presidential election between Franklin D. Roosevelt and Alf Landon, the Literary Digest received 2.3 million mail-in ballots that it used to predict the results: a landslide in favor of Landon. Clearly, there has never been a President Landon, so the prediction was incorrect. Why? A)A sample taken only from Literary Digest readers would not necessarily represent the views of the American public in general. B)The survey relied on voluntary responses, which would introduce a bias. C)The survey was subject to nonresponse bias. D)All of the answer options are correct.
D
Each month, the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don't return the form. In one month, responses were obtained from 240,000 of the households contacted. The population of interest is: A)the residents of a suburb who support a new recreation center. B)the 250,000 households contacted. C)only U.S. households with phones. D)all U.S. households.
D
In a study of human development, investigators showed two different types of movies to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. One type of movie was shown at 8 A.M. (right after the children had breakfast) and the other type of movie was shown at 11 A.M. (right before the children were to have lunch). It was found that more crackers were eaten during the movie shown at 11 A.M. than during the movie shown at 8 A.M. The investigators concluded that the different types of movies had different effects on appetite. The results cannot be trusted because: A)the study was not double blind-neither the investigators nor the children should have been aware of which type of movie was being shown. B)the investigators were biased-they knew beforehand what the study would show. C)the investigators should have used several bowls, with crackers randomly placed in each. D)the time each movie was shown is a confounding variable.
D
Researchers must be cautious when designing web-based surveys, because these surveys are particularly sensitive to: A)voluntary response bias. B)undercoverage. C)nonresponse. D)All of the answer options are correct.
D
To assess the opinion of students at The Ohio State University about campus safety, a reporter for the student newspaper interviews 15 students that she meets walking on the campus late at night who are willing to give their opinion. The sample obtained is: A)a simple random sample of students feeling safe. B)a stratified random sample of students feeling safe. C)a probability sample of students with night classes. D)probably biased.
D
Veterinarians often use nonsteroidal anti-inflammatory drugs to treat lameness in horses. A group of veterinary researchers wanted to find out how widespread the practice is in the United States. They obtained a list of all veterinarians treating large animals, including horses. They sent questionnaires to all the veterinarians on the list. Such a survey is called a census. The response rate was 40%. Which of the following statements is not correct? A)Such a low response rate has the potential for response bias. B)The intended sample consisted of the target population. C)The chance to be selected into the sample was the same for all veterinarians. D)The sample was a volunteer sample.
D
Which of the following might cause undercoverage of older people in surveys of the general population? A)online surveys B)surveys that employ randomly dialed cell phone numbers C)surveys conducted at shopping malls D)All of the answer options are correct.
D
Will a fluoride mouthwash used after brushing reduce cavities? Twenty sets of twins were used to investigate this question. One member of each set of twins used the mouthwash after brushing, and the other did not. After six months, the difference in the number of cavities for those using the mouthwash was compared with the number of cavities for those who did not use the mouthwash. This experiment uses: A)random placeboes. B)double blinding. C)double replication. D)a matched pairs design.
D
A researcher studying the effect of price cuts on consumers' expectations makes up two different histories of the store price of a hypothetical brand of laundry detergent for the past year. Eight students in a business class view one or the other price history on a computer. Some students see a steady price, whereas others see regular sales that temporarily cut the price. Students are asked the price they would expect to pay. The response is: A)the laundry detergent. B)the eight business students. C)the price the students would expect to pay. D)the sale prices.
c