This is another bias that can occur with social science surveys. People want to be agreeable so they are more likely to answer in the affirmative to a "yes/no" or "agree/disagree" question — particularly if they are less-educated or have less information. One way to get around this bias is to ask participants to choose between two statements (the forced choice format) rather than have them agree or disagree to one statement. The two statements would give two different views of a subject.
And in addition to being agreeable, survey respondents also want to be seen as likeable. "Research has shown that respondents understate alcohol and drug use, tax evasion and racial bias; they also may overstate church attendance, charitable contributions and the likelihood that they will vote in an election," notes Pew Research. Therefore, the questions have to be framed in a way that gives participants an "out" for admitting to less-than-desirable behavior. So, a question on voting could be phrased as: "In the 2012 presidential election between Barack Obama and Mitt Romney, did things come up that kept you from voting, or did you happen to vote?"