Practice test 4

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" (two cups of coffee) and all students in the 9:30 section are not permitted to have any caffeine before a mid-term exam. Suppose half of the 8:30 students are randomly allocated to the treatment group (two cups of coffee), the other half to the control group (two cups of decaf). In addition, half of the 9:30 students are randomly allocated to the treatment group, the other half to the control group. This is an example of a A. voluntary response study B. stratified sampling procedure C. matched pairs design D. completely randomized design E. block design

E. block design

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. systematic random sample B. stratified random sample C. multistage sample D. simple random sample E. cluster sample

B. stratified random sample

Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" (two cups of coffee) and all 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 9:30 classes have different instructors. This is an example of A. placebo effect B. bias C. confounding D. observational study E. stratification

C. confounding

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 33547 72450 16632 81194 14873 The first three students in your sample have labels A. 955, 929, 400 B. 400, 769, 769 C. 559, 294, 007 D. 929, 400, 769 E. 400, 769, 335

E. 400, 769, 335

The most important advantage of experiments over observational studies is that A. experiments are usually easier to carry out B. experiments can give better evidence of causation C. confounding cannot happen in experiments D. an observational study cannot have a response variable E. observational studies cannot use random samples

B. experiments can give better evidence of causation

A researcher for a consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that will use the company's current detergent formula. The most important reason for this random assignment is that A. randomization B. randomization eliminates the impact of any confounding variables C. randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups D. randomization ensures that the study is double-blind E. randomization reduces the impact of outliers

C. randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups

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

C. reduces sampling variability

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. allows double-blinding C. reduces sampling variability D. creates approximately equal groups for comparison E. eliminates the placebo effect

D. creates approximately equal groups for comparison

An example of a nonsampling error that can reduce the accuracy of a sample survey is A. using voluntary response to choose the sample B. using the telephone director as the sampling frame C. interviewing people at shopping malls to obtain a sample D. variation due to chance in choosing a sample at random E. many members of the sample cannot be contacted

E. many members of the sample cannot be contacted

If changes in a response variable are due to the effects of the explanatory variable as well as the effects of lurking variables, and we cannot distinguish between these effects, we are said to have A. a cause-and-effect relation between the explanatory and response variables B. a placebo effect C. confounding D. correlation E. extrapolated

C. confounding

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

D. cluster sample

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

A. a block design

Frequently, telephone poll-takers call near dinner time- between 6 pm and 7 pm- because people are at home then. This is an effort to avoid A. voluntary response bias B. calling people after they have gone to bed C. a convenience sample D. nonresponse E. response bias

D. nonresponse

The Bradley effect is a theory proposed to explain observed discrepancies between voter opinion polls and election outcomes in some elections where a white candidate and a non-white candidate run against each other. The theory proposes that some voters tend to tell pollsters that they are undecided or likely to vote for a non-white candidate, and yet, on Election Day, vote for the white opponent. This is an example of A. voluntary response bias B. bias resulting from question wording C. undercoverage D. nonresponse E. response bias

E. response bias

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

A. distinguishes a treatment effect from the effects of confounding variables

An experiment was conducted by some students to explore the nature of the relationship between a person's heart rate (measured in beats per minute) and the frequency at which that person stepped up and down on steps of various height. Three rates of stepping and two different step heights were used. A subject performed the activity (stepping at one of the three stepping rates at one of the two possible heights) for three minutes. Heart rate was then measured at the end of this period. The variables "stepping rate" and "step height" are the A. factors B. levels C. controls D. units E. response variables

A. factors

A study of elementary school children, ages 6 to 11, finds a high positive correlation between shoe size x and score y on a test of reading comprehension. The observed correlation is most likely due to A. the effect of a lurking variable, such as age B. a mistake, since the correlation must be negative C. cause and effect (larger shoe size causes higher reading comprehension) D. "reverse" cause and effect (higher reading comprehension causes larger shoe size E. several outliers in the data set

A. the effect of a lurking variable, such as age

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 the sample size is too small C. nothing, because there is no control group for comparison D. that the new treatment is better than aspirin E. that the remedy is not effective for the treatment of headaches

C. nothing, because there is not control group for comparison

Simple random sampling A. reduces bias resulting from poorly worded questions B. offsets bias resulting from undercoverage and nonresponse C. reduces bias resulting from the behavior of the interviewer D. reduces variability E. None of the above

E. None of the above

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

E. exam performance

Are dogs better at tracking the movements of brightly colored objects? Fifteen experienced "disk dogs" who have been trained to catch flying disks in mid-air are given the chance to catch a bright red disk or a plain white disk. Each disk is thrown 10 times for each dog, with the sequence of disks (red or white) determined randomly. The proportion of red disks caught to the proportion of white disks caught is compared for each dog. This is an example of a A. simple random sample B. stratified random sample C. completely randomized design D. matched pairs design E. double-blind design

D. matched pairs design