Unit 4 Practice of Statistics MC Exam A

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

• that the remedy is effective for the treatment of headaches

• nothing, because the sample size is too small

• nothing, because there is no control group for comparison

• that the new treatment is better than aspirin

• that the remedy is not effective for the treatment of headaches

We wish to draw a sample of 5 without replacement from a population of 50 households. Suppose the households are numbered 01, 02, ..., 50 and suppose that the relevant line of the random number table is 11362 35692 96237 90842 46843 62719 64049 17823.

Then the households selected are

• 11 13 36 62 73

• 11 36 23 08 42

• 11 36 23 23 08

• 11 36 23 56 92

• 11 35 96 90 46

A maple sugar manufacturer wants to estimate the average trunk diameter of Sugar Maple trees 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 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

• multistage sample

• stratified sample

• simple random sample

• cluster sample

• convenience sample

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

• randomization makes the analysis easier since the data can be collected and entered into a computer in any order

• randomization eliminates the impact of any confounding variables

• 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

• randomization ensures that the study is double blind

• randomization reduces the impact of outliers

To test the effectiveness 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, the work without music. The order of the two treatments for each worker is determined randomly. This is

• an observational study

• a matched pairs experiment

• a completely randomized design

• a block design, but not a matched pairs design

• impossible to classify unless more details of the study are provided

A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and made by companies based in Japan. A random sample of 25 cars from a student parking lot at Lee-Davis High School was taken. Which of the following statements is NOT correct?

• This sample may not be representative of the cars in Mechanicsville because mainly students park at Lee-Davis High School

• If the particular parking space is vacant, we can simply select another parking space at random because it is unlikely that a space being vacant is related to the color or manufacturer of the car

• It would be an error to simply select the first 25 parking spaces in the lot closest to the auditorium because there are a number of spaces there reserved for Drivers Ed vehicles, whose primary color is white

• A different team doing the sampling independently would obtain different answers for their sample proportions

• The results will be the same regardless of the time of day that the sample was taken

A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Vitamin C is measured in milligrams per 100 milligrams of fruit. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively:

• A specific storage time, amount of vitamin C, a fruit pack

• A fruit pack, amount of vitamin C, a specific storage time

• Random assignment, a fruit pack, amount of vitamin C

• A specific storage time, a fruit pack, amount of vitamin C

• A specific storage time, the nutritionist, amount of vitamin C

A researcher observes that, on average, the number of divorces in cities with Major League Baseball teams is larger than in cities without teams. The most plausible explanation for this observed association is that the

• presence of a Major League Baseball team causes the number of divorces to rise (perhaps husbands are spending too much time at the ballpark)

• high number of divorces is responsible for the presence of Major League Baseball teams (more single men means potentially more fans at the ballpark, making it attractive for an owner to relocate to such cities)

• 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 divorces)

• association makes no sense, since many married couples go to the ballpark together

• observed association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental

Control groups are used in experiments in order to

• control the effects of outside variables on the outcome

• control the subjects of a study to ensure that all participate equally

• guarantee that someone other than the investigators, who have a vested interest in the outcome, controls how the experiment is conducted

• achieve a proper and uniform level of randomization

• reduce the variability in results

A survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salaries of women and men. For a random sample of graduates, three variables are to be recorded: gender, starting salary, and area of specialization. Which of the following best describes a conclusion that can be drawn from this study?

• Whether being female causes graduates of this nursing school to have lower (or higher) starting salaries than males

• Whether being female causes graduates in this sample to have lower (or higher) starting salaries than males

• Whether choosing a certain area of specialization causes female graduates of this nursing school to have lower (or higher) starting salaries than males

• Whether there is an association between gender and starting salary among graduates of this nursing school

• Whether there is an association between gender and starting salary at all nursing schools similar to this one