1. Discover magazine once reported that 90 percent of the passengers who survived airplane crashes had thought ahead of time about how they would exit the plane if it crashed. The magazine recommended that all passengers do likewise. Why do the data they cite not provide persuasive support for their recommendation?
2. Identify each of the following errors in a public opinion survey as either sampling error or systematic error:
a. The survey misses many people who work during the day.
b. The survey interviews only randomly selected people.
c. The survey is conducted at McDonald's.
d. The survey is conducted in a large apartment building.
3. Identify each of the following errors as either sampling error or systematic error:
a. A study of income misses people whose income is not reported to the government.
b. People tend to over report their income in surveys.
c. A study of after-tax income looks at take-home pay without considering tax refunds.
d. A random sample might not select the person with the highest income.
4. Explain why the following procedure is likely to produce either biased or unbiased estimates of the amount of money people spend at restaurants each year. A random number between 1 and 7 is selected; this turns out to be 6. The survey then begins on January 6 and is conducted every 7 days for a full year: January 6, January 13, January 20, and so on.