Unit 3 MCQ Review

Which of the following is the best description of a simple random sample of size n from a population of size N?

A sampling method in which every individual is equally likely to be selected.

Some studies of the relationship between car color and frequency of accidents have found that red cars are more likely to be in accidents than black cars, despite how visible they are. Some experts warn that we should not conclude that red cars are less safe than black cars, because of possible confounding. Which of the following best describes what this means?

Studies of this type are all observational, and it is not possible to separate the effect of car color from the type of people who choose to drive red cars.

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. Forty-four percent 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. The experimental units are the

The 100 adults that volunteered.

A political action committee sends out a questionnaire to randomly-selected mailing addresses, asking people to rate the importance of a variety of economic and social issues facing the country. At the end of the questionnaire is an (optional) invitation to donate money to the political action committee. Which of the following statements about this survey is true?

The survey results will overestimate support for this political action committee in the entire population because people are more likely to respond if they are prepared to donate money.

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: sex, starting salary, and area of specialization. Which of the following best describes a conclusion that can be drawn from this study?

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

A farmer wishes to determine which of two brands of baby pig pellets, Kent or Moormans, produces better weight gains. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B. The farmer has conducted a(n)

experiment, but not a completely randomized experiment.

We say that the design of a study is biased if

it systematically favors certain outcomes over others.

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

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.

Mr. Eyabi wants to know, does caffeine improve exam performance? 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

randomized block design.

A public opinion poll in Ohio wants to determine if 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

stratified random sample. The method of sampling from a population which can be partitioned into subpopulations.