Q2 Practice Quiz 2 Stats

In a recent poll of 1,500 randomly selected eligible voters, only 525 (35%) said they did not vote in the last election. However, a vote count showed that 80% of eligible voters actually did not vote in the last election. Which of the following types of bias is most likely to have occurred in the poll? A) Selection bias B) Sampling bias C) Nonresponse bias D) Uncoverage bias E) Response bias

Response bias

Which among the following is most useful in establishing cause-and-effect relationships? A) A complete census B) A least squares regression line showing high correlation C) A simple random sample D) A well-designed, well-conducted survey E) A controlled experiment

a controlled experiment

Which of the following is not a property of a large table of random digits? A) The contents of one section of the table are independent of other sections of the table. B) Each digit 0 through 9 occurs with equal frequency. C) Each three-digit number 000 through 999 occurs with equal frequency. D) The table will contain, somewhere, the sequence 1234. E) Consecutive rows do not start with the same digit.

consecutive rows do not start with the same digit

Which of these best explains why large samples tend to provide more reliable inferences about a population than small samples? A) Large samples show less sampling variability. B) The response variable will be measured more effectively. C) It will be less of a problem if the randomization is imperfect. D) There is a smaller probability of bias. E) Large samples are more diverse.

large samples show less sampling variability

A 2008 ballot initiative in California sought a constitutional ban on same sex marriage. Suppose a survey prior to the election asked the question, "Do you favor a law that would eliminate the right of same sex couples to marry?" This question could produce biased results. Which of the following is the most likely reason? A) Same sex couples are likely to be underrepresented in the sample. B) The wording of the question could influence the response. C) Only those who feel strongly about the issue are likely to respond. D) Not all registered voters who respond to the survey are likely to vote. E) Married couples are likely to vote the same way.

the wording of the question could influence the response

Which of the following is a method for improving the accuracy of a sample? a. use smaller sample sizes b. when possible, avoid the use of human interviewers, relying on computerized dialing instead c. use larger sample sizes d. use no more than 3 or 4 words in any question

use larger sample sizes

A manufacturer wants to test a sample of the products his company produces. Products are produced in sets of 100, and each set of 100 is called a lot. The company produces hundreds of lots each day. The manufacturer decides to randomly select five lots from each day's production run and test every product in these five lots. Which of the following best describes this type of sampling? A) Convenience B) Simple random C) Stratified random D) Cluster E) Systematic

Cluster

For a certain experiment you have 8 subjects, of which 4 are female and 4 are male. The names are Males: Atwater, Bacon, Chu, Diaz Females: Johnson, King, Liu, Moore. There are two treatments, A and B. If a randomized block design is used, with the subjects blocked by their gender, which of the following is NOT a possible group of subjects who receive treatment A? A) Atwater, Bacon, Johnson, King B) Atwater, Diaz, Liu, King C) Atwater, Chu, King, Liu D) Bacon, Chu, Liu E) Atwater, Bacon, Chu, Johnson

Atwater, Bacon, Chu, Johnson

Treatment of breast cancer is a controversial issue with treatment varying from radical mastectomy to radiation and chemotherapy combined with simple lumpectomy. One long-term study involved noting survival times of all breast cancer patients from over 100 hospitals and comparing the percentage of women still alive 5 years after radical mastectomies with the percentage of women still alive 5 years after radiation and chemotherapy combined with simple lumpectomy. The results seems to show a better outcome for women who received lumpectomy treatment. Which of the following statements are appropriate? I. This appears to be a well-conducted controlled experiment. II. This observational study should be faulted for a lack of blinding. III. A lurking variable involving who received what treatment makes any conclusion suspect. A) I only B) II only C) III only D) I and II E) II and III

III only

A nutritional consulting company is trying to find what percentage of the population of a town is overweight. The marketing department contact by telephone 600 people from a list of the entire town's population. About 100 people give answers to the survey. Which of the following is the most significant source of bias in this survey? A) Undercoverage B) Response bias C) Size of sample D) Nonresponse E) Voluntary response bias

Nonresponse

In which of the following situations would it be most difficult to use a census? A) To determine what proportion of registered students enrolled in a college are employed more than 20 hours each week. B) To determine what proportion of fish in Lake Michigan are bass. C) To determine what proportion of single-family dwellings in a small town have two-car garages. D) To determine what proportion of licensed bicycles on a university campus have lights. E) To determine what proportion of students in a high school support wearing uniforms.

To determine what proportion of fish in Lake Michigan are bass

Which of the following is not a characteristic of stratified random sampling? A) The population is divided into groups that are similar on some characteristic. B) Random sampling is part of the sampling procedure. C) Each individual unit in the population belongs to one and only one of the strata. D) Every possible subset of the population, of the desired sample size, has an equal chance of being selected. E) The strata are based on facts known before the sample is selected.

every possible subset of the population, of the desired sample size, has an equal chance of being selected

A recent survey by a large-circulation Canadian magazine on the contribution of universities to the economy was circulated to 394 people who the magazine decided "are the most likely to know how important universities are to the Canadian economy." The main problem with using these results to draw conclusions about the general public's perception is a. insufficient attention to the placebo effect b. response bias c. no control group d. lack of random selection e. lack of random assignment

lack of random selection

An experiment to measure the effect of giving hormones to girls affected by Turner's Syndrome was carried out recently in Vancouver. All 34 girls in the study were given the growth hormone and their heights were measured at the time the hormone was given and again one year later. No measurements were made on their final adult heights. Which of the following is not a problem with this experiment: A) There was no control group. B) Nonresponse bias C) There was insufficient attention to the placebo effect. D) Because final heights were not measured, it is impossible to tell if the hormone affected final height or only accelerated growth and made no difference to final height. E) There was no blinding.

nonresponse bias

The editor of the newspaper at a large university wants to measure student opinion on a proposed change in graduation requirements. The editor randomly selects 100 freshman, 100 sophomores, 100 juniors and 100 seniors to take a short survey. This plan is an example of what kind of sampling? A) Systematic sampling B) Stratified random sampling C) Convenience sampling D) Simple random sampling E) Cluster sampling

stratified random sampling

A cause-and-effect relationship between two variables can best be determined from which of the following? A) A controlled experiment where the observational units are assigned randomly. B) When the two variables have a correlation coefficient near 1. C) A survey conducted using a simple random sample of individuals. D) An observational study where the observational units are chosen randomly. E) A survey conducted using a stratified random sample of individuals

a controlled experiment where the observational units are assigned randomly

A researcher observes that, on average, the number of traffic violations in cities with Major League Baseball teams is larger than in cities without Major League baseball teams. The most plausible explanation for this observed association is that the A) presence of a Major League baseball team causes the number of traffic incidents to rise (perhaps due to the large number of people leaving the ballpark.) B) association is due to the presence of a lurking variable. (Major League teams tend to be in large cities with more people, hence a greater number of traffic incidents) C) observed association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental. D) association makes no sense, since many people take public transit or walk to baseball games. E) high number of traffic incidents is responsible for the presence of Major League baseball teams (more traffic incidents means more people have cars, making it easier for them to get to the ballpark.)

association is due to the presence of a lurking variable. (Major League teams tend to be in large cities with more people, hence a greater number of traffic incidents)

A drug company wishes to test a new drug. A researcher assembles a group of volunteers and randomly assigns them to one of two groups -- one to take the drug and one to take a placebo. In addition, the company wants the experiment to be double-blinded. What is the meaning of double-blind in this situation? A) Neither the volunteers nor the drug company executives know which volunteers are take the drug and which are taking the placebo. B) Neither the volunteers nor the evaluator know which volunteers are taking the drug and which are taking the placebo. C) The volunteers in both groups do not know whether they are taking the drug or the placebo. D) The volunteers in both groups are blindfolded when they take the drug or placebo. E) As long as the subjects are randomly assigned to the two groups, there is no need to make the experiment double-blinded.

neither the volunteers nor the evaluator know which volunteers are taking the drug and which are taking the placebo

An experimenter believes that two new exercise programs are more effective than any current exercise routines and wishes to compare the effectiveness of these two new exercise programs on physical fitness. The experimenter is trying to determine whether or not a control group which follows neither of these new programs but continues with current exercise routines would be beneficial. Which of the following can be said about the addition of a control group? A) A control group would allow the experimenter to determine which of the two exercise programs improves physical fitness the most. B) A control group would eliminate the need for blinding in the study. C) There would be no added benefit to having a control group. D) A control group would eliminate the placebo effect. E) A control group would allow the experimenter to determine if either of the exercise programs is more effective than current programs for physical fitness.

A control group would allow the experimenter to determine if either of the exercise of the programs is more effective than current programs for physical fitness

An advice columnist asks readers to write in about how happy they are in their marriages. The results indicate that 79% of those responding would not marry the same partner if they had to do it all over again. Which of the following statements is most correct? A) It's likely that the results are not accurate because people tend to lie in voluntary surveys. B) It's likely that this result is higher than the true population proportion because persons unhappy in their marriages are more likely to respond. C) There is no way of predicting whether the results are biased or not. D) It's likely that this result is lower than the true proportion because persons unhappy in their marriages are unlikely to respond. E) It's likely that this result is an accurate reflection of the population

It's likely that this result is higher than the true population proportion because persons unhappy in their marriages are more likely to respond

A researcher is testing the effect of a new fertilizer on crop growth. He marks 30 plots in a field, splits the plots in half, and randomly assigns the new fertilizer to one half of the plot and the old fertilizer to the other half. After 4 weeks, he measures the crop yield and compares the effects of the two fertilizers. This design is an example of A) This is not an experiment B) Double-blind experiment C) Matched pairs experiment D) Cluster experiment E) Completely randomized comparative experiment

Matched pairs experiment

You want to conduct a survey to determine the types of exercise equipment most used by people at your health club. You plan to base your results on a random sample of 40 members. Which of the following methods will generate a simple random sample of 40 of the members? A) Divide the number of members by 40 to get a value k. Choose one of the first kth names on the list, using a random number generator. Then choose every kth name of the list after that name. B) Get the sign-in lists for each day of the week, Monday through Friday. Randomly choose 8 names from each day for the survey. C) Randomly pick a morning and survey the first 40 people who come in the door that day. D) Put each member's name on a slip of paper and randomly select 40 slips. E) Mail out surveys to every member and use the first 40 that are returned.

Put each member's name on a slip of paper and randomly select 40 slips

To test the effect of music on productivity, a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is A) a matched pairs experiment. B) a completely randomized experiment. C) a block design, but not a matched pairs experiment. D) an observational study. E) impossible to classify unless more details of the study are provided.

a matched pairs experiment

Which of the following is an appropriate sample for a study interested in the average interest rates of home loans from a national bank? a. thousands of loan rates from all branches in the Midwest b. loan rates from ten of your neighbors who bank at the local branch c. a random sample of one thousand loan rates d. all loan rates from all branches in one town and a random sample of loan rates from other areas of branches e. less than one hundred loan rates from one brain in a town

a random sample of one thousand loan rates

Which of the following is the best description of a systematic random sample? A) After a population is separated into distinct groups, one or more of these groups are randomly selected in their entirety to be the sample. B) A sample chosen in such a way that every possible sample of a given size has an equal chance to be the sample. C) A value is randomly selected from an ordered list and then every nth value in the list after that first value is selected from the sample. D) A sample in which respondents volunteer their response. E) Select a sample in such a way that the proportion of some variables thought to impact the response is approximately the same in the sample as in the population.

a value is randomly selected from an ordered list and every nth value in the list after that first value is selected from the sample

40% of the staff in a local school district have a master's degree. One of the schools in the district has only 4 teachers out of 15 with a master's degree. You are asked to design a simulation to determine the probability of getting this few teachers in a group this size. Which of the following assignments of the digits 0 through 9 would be appropriate for modeling this situation. A) Assign 0, 1, 2, 3 as having a master's degree and 4, 5, 6, 7, 8, 9 as not having a degree. B) Assign 0, 1 as having a master's degree and 2, 3, 4, 5, 6, 7, 8, 9 as not having a degree. C) Assign 0, 1, 2 as having a master's degree and 4, 5, 6, 7, 8, 9 as not having a degree. D) Assign 1, 2, 3, 4, 5 as having a master's degree and 0, 6, 7, 8, 9 as not having a degree. E) Assign 7, 8, 9 as having a master's degree and 0, 1, 2, 3, 4, 5, 6 as not having a degree.

assign 0, 1, 2, 3 as having a master's degree and 4, 5, 6, 7, 8, 9 as not having a degree

A study randomly assigned patients to treatment groups to determine the effect of taking aspirin in preventing the development of colon polyps. One group took an aspirin daily and the other group took a placebo. Neither the patients nor the doctors knew who was getting which pill. This study is best described as a A) Blinded block design observational study B) Randomly assigned observational study C) Block design with random assignment D) Blind experiment with random assignment E) Double-blind comparative experiment

double-blind comparative experiment

Since many individuals walk around their homes in their socks, a manufacturer has created a material for socks that is believed to be more resistant to wear than cotton. The manufacturer wishes to test this belief over a period of a month. Given a group of volunteers, which of the following designs will best test this new material's resistance to wear? A) Have the volunteers wear the socks made from the new material for a month, and check the wear on the socks at the end of the month. B) Allow half of the volunteers to wear cotton socks, while the other half wear socks made of the new material. Compare the wear on the socks at the end of the month. C) For each volunteer, randomly choose which foot wears a cotton sock, while the other foot wears a sock made of the new material. Compare the wear on the socks at the end of the month. D) Randomly assign half of the volunteers to wear cotton socks, while the other half wear socks made of the new material. Compare the wear on the socks at the end of the month. E) Randomly assign half of the volunteers to wear cotton socks, while the other half wear socks made of the new material. At the end of two weeks, the volunteers should change sock types. Compare the wear on the socks at the end of the month.

for each volunteer, randomly choose which foot wears a cotton sock, while the other foot wears a sock made of the new material. compare the wear on the socks at the end of the month

To survey the opinions of the students at your high school, a researcher plans to select every twenty-fifth student entering the school in the morning. Assuming there are no absences, will this result in a simple random sample of students attending your school? A) No, because not every sample of the intended size has an equal chance of being selected. B) Yes, because 24 out of every 25 students who are not selected will form a control group. C) Yes, because this is an example of systematic sampling, which is a special case of simple random sampling. D) Yes, because every student has the same chance of being selected. E) Yes, but only if there is a single entrance to the school.

no, because not every sample of the intended size has an equal chance of being selected

A test run to compare two statistics textbooks, one with a traditional approach and one with a new approach. A state university agrees to use the traditional text in all of its 30 classes, each with approximately 50 students. A private liberal art college agrees to use the new approach text in its 4 statistics classes, each with 20 students. A SRS of 30 statistics students at each school will take a standardized final exam, and the mean scores of the two groups will be compared. Is this a good experimental design? A) Yes, because it uses randomization and blocking. B) No, because proportions of students passing would be more appropriate. C) No, because so many more students take statistics at the university. D) No, because the exam should have been given to all the students. E) No, because there is a confounding variable: different kinds of schools

no, because there is a confounding variable: different kinds of schools

A new cough medicine was given to a group of 25 subjects who had a cough due to the common cold. Thirty minutes after taking the new medicine, 20 of the subjects reported that their coughs had disappeared. From this information, you conclude A) That the remedy is effective for the treatment of coughs. B) Nothing, because there is no control group for comparison. C) That the treatment is better than the old medicine. D) Nothing, because the sample size is too small. E) That the remedy is not effective for the treatment of coughs.

nothing, because there is no control group for comparison

A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude: A) that the remedy is effective for the treatment of headaches. B) nothing, because there is no control group for comparison. C) that the remedy is not effective for the treatment of headaches. D) nothing, because the sample size is too small. E) that the new treatment is better than aspirin.

nothing, because there is no control group for comparison

A randomized block design will be used in an experiment to compare two lotions that protect people from getting sunburned. Which of the following should guide the formation of the blocks? A) Participants should be kept blind as to which block they are in. B) Participants should be randomly assigned to blocks. C) Participants in the same block should receive the same lotion. D) Participants within each block should be as similar as possible with respect to how easily they get sunburned. E) Participants with each block should be as different as possible with respect to how easily they get sunburned.

participants within each block should be as similar as possible with respect to how easily they get sunburned

A television news editor would like to know how local registered voters respond to the question: "Are you in favor of the school bond measure that will be voted on in an upcoming special election?" A television survey is conducted during a break in the evening news by listing two telephone numbers side by side on the screen, one for viewer to call if they approve of the bond measure, and the other to call if they disapprove. This survey method could produce biased results for a number of reasons. Which of the following is the most obvious reason? A) It uses a stratified sample rather than a simple random sample. B) People who feel strongly about the issue are more likely to respond. C) Some registered voters who call might not vote in the election. D) Viewers should be told about the issues before the survey is conducted. E) The wording of the question is biased.

people who feel strongly about the issue are more likely to respond

A researcher is testing a company's new stain remover. He has contracted with 40 families who have agreed to test the product. He randomly assigns 20 families to the group that will use the new stain remover and 20 to the group that will use the company's current product. The most important reason for this random assignment is a. randomization is a good way to create two groups of 20 families that are as similar as possible except for the treatments they receive b. randomization makes the analysis easier since the data can be collected and entered into the computer in any order c. randomization eliminates the impact of any confounding variables d. randomization reduces the impact of outliers e. randomization ensures that the study is double-blinded

randomization is a good way to create two groups of 20 families that are as similar as possible except for the treatments they receive

A civil engineer is testing the reliability of traffic signal controllers produced by two different companies. He has 20 sets of controllers from each company, and he has been given clearance to install them at 40 different intersections in the city. He randomly assigns the controllers from company A to 20 intersections and the controllers from company B to the other intersections. The most important reason for this random assignment is that A) randomization makes the analysis easier since the data can be collected and entered into the computer in any order. B) randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups. C) randomization eliminates the impact of any confounding variables. D) randomization reduces the impact of outliers. E) randomization ensures that the study is double-blind.

randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups

Which of the following is a true statement about experimental design? A) The placebo effect is a concern for all experiments. B) Blocking eliminates the effects of all lurking variables. C) Control is a key component in experimental design. Thus, a control group that receives a placebo is a requirement for experimentation. D) Replication is a key component in experimental design. Thus an experiment needs to be conducted on repeated samples before generalizing results. E) Randomization is a key component in experimental design. Randomization is used to reduce bias.

randomization is a key component in experimental design. randomization is used to reduce bias

The owner of a factory that employs half the citizens in a small town is trying to decide whether to take a public stand on a controversial issue. He realizes that he would benefit from knowing how the townspeople feel. He randomly selects 50 of the townspeople from a list of all the town's population. He personally contacts all 50 and asks them their opinion on the issue. Most give him an answer, but 12 townspeople decline to participate. He decides to summarize his results based on the 38 responses. Which of the following list the most significant sources of bias in this survey? A) Response bias and undercoverage B) Response bias and nonresponse C) Voluntary response bias and nonresponse D) Nonresponse and undercoverage E) Voluntary response bias and undercoverage

response bias and nonresponse

Which of the following statements is false? A) Sophisticated statistical methods can always correct the results if the population you are sampling from is different from the population of interest, for example, due to undercoverage. B) Slight changes in the wording of questions can make a measurable difference in survey results. C) Non-sampling errors can distort the results of a census. D) People will sometimes answer a question differently for different interviewers. E) Nonresponse can cause bias in surveys because nonrespondents often tend to behave differently than people who respond.

sophisticated statistical methods can always correct the results if the population you are sampling from is different from the population of interest, for example, due to undercoverage

A US government researcher wants to select a sample of tax returns that will include returns from a variety of different income levels. He divides the set of all the different incomes shown on the forms into 10 non-overlapping ranges. Then he randomly selects 100 tax returns from each. Which of the following best describes the sampling scheme used in this example? A) Simple random sampling B) Two-stage sampling C) Stratified random sampling D) Convenience sampling E) Cluster sampling

stratified random sampling

A company with offices in 5 different countries is interested in estimating the proportion of its employees in favor of banning smoking on the office premises. It is known that the views of people from different countries on issues like smoking tend to vary due to the influence of different local social structures. Which of the following is an appropriate sampling technique to use in this situation, and why? A) Cluster sample, because the population is divided into 5 clusters -- name 5 offices in 5 countries. B) Stratified sample, because the population is divided into 5 strata -- namely 5 offices in 5 countries. C) Simple random sample, because this is the simplest sampling method. D) Simple random sample, because this is the only method for which inferential techniques are available. E) Simple random sample, because this is the only method that gives unbiased results.

stratified sample, because the population is divided into 5 strata -- namely 5 offices in 5 countries

Which of the following situations is a cluster sample? a. survey five friends concerning their opinions of a local hockey team b. from a list of all students in your school, randomly select 20 to answer a survey about internet use c. identify four ethnic groups at your school. From each group, choose enough respondents so that the final sample contains roughly the same proportion of each group as the school population d. take a random sample of five voting precincts in a large metropolitan area and do an exit poll at each voting site e. measure the length of time each fifth person entering a restaurant has to wait to be seated

take a random sample of five voting precincts in a large metropolitan area and do an exit poll at each voting site

Which of the following best describes a cluster sample of size 20 from a population of size 300? A) Each of the 320 people is assigned a number. Twenty numbers are randomly selected by a computer and the people corresponding to these 20 numbers are the sample B) The sample will consist of the first 20 people who volunteer to be part of the sample. C) The 320 names are put into an alphabetical list and the list numbered from 1 to 320. A number between 1 and 304 (inclusive) is selected at random. The person corresponding to that number and the next 19 people on the list are selected for the sample. D) The 320 names are put into an alphabetical list. One of the first 16 names on the list is selected at random as part of the sample. Every 16th name on the list is then selected for the sample. E) All 320 names are written on slips of paper and the slips are put into a box. Twenty slips are selected at random from the box.

the 320 names are put into an alphabetical list and the list numbered from 1 to 320. a number between 1 and 304 (inclusive) is selected at random. the person corresponding to that number and the next 19 people on the list are selected for the sample

Random error and bias error are two kinds of sampling errors. Which of the following is true about bias error? A) It is a pattern of errors that tend to cancel one another out so that the overall result still accurately reflects the true value. B) Bias error refers to sample takers who have a problem with bigotry. C) Every sample design will generate a certain amount of random error. D) The pattern of errors is loaded in one direction and therefore do not balance each other out, producing a true distortion.

the patterns of errors is loaded in one direction and therefore do not balance each other our, producing a true distortion

For which of the following purposes would it be most unreasonable to use a census? A) To determine the proportion of red snappers with a high mercury level in the Gulf of Mexico. B) To determine the mean wage earned by construction workers in a small town. C) To determine the mean selling price of houses in your neighborhood. D) To determine the proportion of students with a learning disability in a small rural area high school. E) To determine the difference between the proportion of engineering professors and the proportion of business professors in favor of the new teaching initiative at a large university.

to determine the proportion of red snappers with a high mercury level in the Gulf of Mexico

Approximately 52% of all recent births were boys. In a simple random sample of 100 recent births, 49 were boys and 51 were girls. The most likely explanation for the difference between the observed results and the expected results in this case is A) variability due to sampling B) bias C) nonsampling error D) confounding E) a sampling frame that is incomplete

variability due to sampling

You want to do a survey of members of the senior class at your school and want to select a simple random sample. You intend to include 40 students in your sample. which of the following approaches will generate a simple random sample? A) Randomly select 10 students from each of the four senior calculus classes. B) Write the name of each student in the senior class on a slip of paper and put the papers in a container. Then randomly select 40 slips of paper from the container. C) From a list of all seniors, select one of the first 10 names at random. Then select every nth name on the list until you have 40 people selected. D) Assuming that students are randomly assigned to classes, select two classes at random and include those students in your sample. E) Select the first 40 seniors to pass through the cafeteria door at lunch.

write the name of each student in the senior class and put the papers in a container. then randomly select 40 slips of paper from the container