Chapter 4 Test 1

A stratified random sample is appropriate when... A. it is impractical to take a simple random sample because the population is too large B. the population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is quite different within the groups but very similar between the groups C. the population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between the groups D. you want to avoid under coverage of certain groups E. you intend to take a sample of more than 100 individuals

C. the population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between the groups

A maple sugar manufacturer wants to estimate the average trunk diameter of Sugar Maple tress in a large forest. There are too many trees to list them all and take an SRS, so he divides the forest into several hundred 10m X 10m plots, selects 25 plots at random, and measures the diameter of every single tree in each one. This is an example of... A. multistage sample B. convenience sample C. simple random sample D. stratified sample E. cluster sample

E. Cluster sample

You want to take an SRS of 50 of the 816 students who live in a dormitory on campus. You label the students 001 to 816 in alphabetical order. In the table of random digits you read the entries. 95592 94007 69769 333547 70450 16632 81194 14873 The first three students in your sample are: A. 400, 769, 335 B. 929, 400, 769 C. 400, 769, 769 D. 559, 294, 007 E. 955, 929, 400

A. 400, 769, 335

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" (2 cups of coffee) and all the students in the 9:30 section are not permitted to have any caffeine before a mid-term exam. Unfortunately, any systematic difference between the two sections on the exam might be due to the fact that the 8:30 and the 9:30 classes have different instructors. This is an example of what? A. confounding B. bias C. placebo effect D. observational study E. stratification

A. confounding

A public opinion poll in Ohio wants to determine whether or not registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of fifty registered voters from each county in the state and ask whether they approve or disapprove of the measure. This is an example of a... A. stratified random sample B. simple random sample C. systematic random sample D. multistage sample E. cluster sample

A. stratified random sample

Eighty volunteers who currently use a certain brand of over-the-counter allergy medicine have been recruited to participate in a trial of a new allergy medication. The volunteers are randomly assigned to one of two groups. One group continues to take their current medication, the other group switches to the new experimental medication. Each is asked after two weeks if their allergy symptoms are worse, better, or about the same as they were at the start of the study. Which of the following best describes a conclusion that can be drawn from this study? A. We can determine whether the allergies sufferers' symptoms improved more with the new drug than the old drug, but we can't establish cause and effect B. We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study C. We can determine whether the new drug reduces symptoms more than the old drug for anyone who suffers from allergies D. We cannot draw any conclusions, because there was no control group E. We cannot draw any conclusions, since all the volunteers were already taking the old drug when the experiment started

B. We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study

What is a simple random sample? A. a sample that contains the same percent of each subgroup in the population B. any sample that gives every individual the same chance to be selected C. a sample that gives every possible sample of the same size the same chance to be selected D. a sample that selects equal numbers of individuals from each stratum E. any sample selected by using chance

B. any sample that gives every individual the same chance to be selected

The essential difference between an experiment and an observational study is that... A. observational studies cannot have response variables B. in an experiment, people must give their informed consent before being allowed to participate C. an experiment imposes treatments on the subjects, but an observational study does not D. observational studies are always biased E. observational studies may have confounded variables but experiments never do

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

An airline that wants to assess customer satisfaction chooses a random sample of 10 of its flights during a single month and asks all of the passengers on those flights to fill out a survey. This is an example of... A. stratified sample B. simple random sample C. cluster sample D. convenience sample E. multistage sample

C. cluster sample

The principle reason for the use of controls in designing experiments is that it... A. reduces sampling variability B. allows for double-binding C. distinguishes a treatment effect from the effects of confounding variables D. eliminates the placebo effect E. creates approximately equal groups for comparison

C. distinguishes the treatment effect from the effects of confounding variables

In order to assess the effects of exercise on reducing cholesterol, a researcher took a random sample of fifty people from a local gym who exercised regularly. They all reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether or not the subjects exercised regularly. Which of the following best describes the inferences the researcher can make based on his results? A. There is not enough information to make judgements about the scope of the inference B. He can make inferences about cause and effect, but not about the population from which the samples were taken C. He cannot make inferences about either cause and effect or the population from which the samples were taken D. He can make inferences about the population from which the samples were taken, but not about cause and effect E. He can make inferences about both cause and effect and the population from which the samples were taken

D. He can make inferences about the populations form which the samples were taken, but not about cause and effect

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" (2 cups of coffee) and all the students in the 9:30 section are not permitted to have any caffeine before a mid-term exam. What is the response variable of the study? A. the exam performance B. the time the class is held C. teacher's performance D. two cups of coffee E. class attendance

A. exam performance

One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other fifty are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of depression. The study would be double blind if... A. all volunteers were not allowed to see the psychiatrist nor the psychiatrist allowed to see the volunteers during the session in which the psychiatrist evaluated the severity of the depression B. neither the volunteers nor the psychiatrist knew which treatment any person had received C. neither drug had any identifying marks on it D. all patients were given a placebo E. all of the above

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

A stratified random sample addresses the same issues as which of the following experimental designs? A. a matched pairs design B. an experiment with a placebo C. a block design D. a confounded, nonrandomized study E. a double-blind experiment

C. a block design

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 completely randomized experiment B. impossible to classify unless more details of the study are provided C. a matched pairs experiment D. an observational study E. a block design, but not a matched pairs experiment

C. a matched pairs experiment

In order to assess the effects of exercise on reducing cholesterol, a researcher took a random sample of fifty people from a local gym who exercised regularly. They all reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether or not the subjects exercised regularly. This is a(n)... A. experiment, but not a double blind experiment B. matched pairs experiment C. observational study D. block design E. double blind experiment

C. observational study

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

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

A sportswriter wants to know how strongly Lafayette residents support the local minor league baseball team, the Lafayette Leopards. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. What is the sample for the survey? A. all people attending the game the day the survey was conducted B. all Leopards fans C. the sportswriter D. the 20 people who gave the sportswriter their opinion E. all residents of Lafayette

D. the 20 people who gave their sportswriter their opinion

In comparative trials in medicine, the placebo effect and subconscious bias on the part of the physicians evaluating the outcomes can be avoided by using... A. response variables B. randomized complete block designs C. stratified random samples D. the double-blind technique E. all of the above

D. the double-blind technique

In an experiment, an observed effect so large that it would rarely occur by chance is called... A. an outlier B. bias C. influential D. replication E. statistically significant

E. statistically significant

A sample of student opinion at a Big Ten university selects an SRS of 200 out of the 30,000 undergraduate students and a separate SRS of 100 of the 5,000 graduate students. This kind of sample is called a... A. simple random sample B. stratified random sample C. random cluster sample D. multistage random sample E. simple random sample with blocking

B. stratified random sample

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

E. All residents of Lafayette

Which of the following is not a major principal of good design for all experiments? A. randomization B. comparison to a control C. blocking D. replication E. all of these are important principals for every experiment

C. blocking

Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers randomly assigned 100 adult volunteers who suffer from allergies to two groups. They gave the new medication to the subjects in one group and an existing medication to the subjects in the other group. 44% of those in the treatment group and 28% of those in the control group reported a significant reduction in their allergy symptoms without any drowsiness. What are the experimental units? A. all the volunteers who did not report a significant reduction in their allergy symptoms without any drowsiness B. pills containing the new experimental medication C. all the volunteers who reported a significant reduction in their allergy symptoms without any drowsiness D. researchers E. 100 adult volunteers

E. 100 adult volunteers

Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers randomly assigned 100 adult volunteers who suffer from allergies to two groups. They gave the new medication to the subjects in one group and an existing medication to the subjects in the other group. 44% of those in the treatment group and 28% of those in the control group reported a significant reduction in their allergy symptoms without any drowsiness. Which of the following best describes the inferences the researchers can make based in his results? A. They cannot make inferences about either cause and affect or the populations from which the samples were taken. B. There is not enough information to make judgements about the scope of the inference. C. They can make inferences about both cause and effect and the populations from which the samples were taken. D. They can make inferences about the population from which the samples were taken but not about cause and effect. E. They can make inferences about cause and effect, but not about the populations from which the samples were taken

E. They can make inferences about cause and effect, but not about the populations from which the samples were taken

A lurking variable is... A. another response variable B. any variable that produces a large residual C. the true variable that is explained by the explanatory variable D. the true cause of a response E. a variable that is not among the variables studied but affects the response variable

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

The principle reason for the use of random assignment in designing experiments is that it... A. distinguishes a treatment effect from the effects of confounding variables B. eliminates the placebo effect C. reduces the sampling variability D. allows double-blinding E. creates approximately equal groups for comparison

E. creates approximately equal groups for comparison