An evaluation of whether people are truthful in their responses to survey questions was conducted in the following manner. In the first survey, 1,000 randomly selected persons were told during a home visit that the survey was being done to obtain information that would help protect the drinking water supply in their city. After the short introduction, they were asked if they used a brand of detergent that was biodegradable. In the second survey, 1,000 randomly selected per-sons were also given the information about safe drinking water during a home visit and then were asked if they used a biodegradable detergent. If they said yes, the interviewer asked to see the box of detergent.
a. What differences do you think will be found in the two estimates of the percentage of households using biodegradable detergents?
b. What types of biases may be introduced into the two types of surveys?