What potential sources of error might be associated with the following situations?

a. In a survey of frequent fliers age 50 and older, researchers concluded that price does not play a significant role in airline travel because only 25 percent of the respondents check off price as the most important consideration in determining where and how they travel.

b. A survey of voters finds that most respondents do not like negative political ads—that is, advertising by one political candidate that criticizes or exposes secrets about the opponent’s “dirty laundry.”

c. Researchers who must conduct a 45-minute personal interview decide to offer $25 to each respondent because they believe that people who will sell their opinions are more typical than someone who will talk to a stranger for 45 minutes.

d. A company’s sales representatives are asked what percentage of the time they spend making presentations to prospects, traveling, talking on the telephone, participating in meetings, working on the computer, and engaging in other on-the-job activities.

e. A survey comes with a water hardness packet to test the hardness of the water in a respondent’s home. The packet includes a color chart and a plastic strip to dip into hot water. The respondent is given instructions in six steps on how to compare the color of the plastic strip with the color chart that indicates water hardness.