A random sample of 500 households was identified in a major North American city using the municipal voter registration list. Five hundred questionnaires went out, directed at one adult in each household, surveying respondents about attitudes regarding the municipal recycling program. Eighty of the 500 surveys were filled out and returned to the researchers.

a. Can the 80 households that returned questionnaires be regarded as a random sample of households? Explain.

b. What type of bias might affect the survey outcome?