1. A market research company wishes to find out whether the population of students at a university prefers brand A or brand B of instant coffee. A random sample of students is selected, and each one is asked to try first brand A and then brand B, or vice versa (with the order determined at random). They then indicate which brand they prefer. The response variable is

A. whether brand A or B is tried first.
B. which brand they prefer.
C. the two brands of coffee.

2. A researcher is interested in the cholesterol levels of adults in the city she lives in. A free cholesterol screening program is set up in the downtown area during the lunch hour. Individuals can walk in and have their cholesterol determined for free. One hundred and seventy-three people use the service and their average cholesterol is 217.8. The sample obtained is an example of

A. a simple random sample since the experimenter did not know beforehand which individuals would come to the screening.
B. a stratified sample of high and low cholesterol individuals.
C. a sample probably containing bias and undercoverage.

3. A sample was taken of the salaries of four employees from a large company. The following are their salaries (in thousands of dollars) for this year.

33    31     24     36

The variance of their salaries is
A. 5.1.
B. 26.
C. 31.