A threat to the quality of questionnaire data, and especially to self-report data from individuals, comes from the various types of response bias, the intentional or unconscious systematic way in which individuals select responses. One of the most common types of response bias, known as social desirability, is answering questions in a manner intended to make a favorable impression (Krumpal, 2013). Social desirability is a powerful motivator and has been widely included in program evaluations in which there is the Potential for the participant to want to please the evaluators or when the participants believe there is a socially correct answer they are supposed to give. Response bias can also occur as a result of the respondent falling into a pattern of giving the same response, regardless of the question or his or her true opinion or feeling. Response bias can be difficult to anticipate. Evaluators would be wise to consider that both response bias and errors inherent in the way the variables are measured can interactively produce questionable or even undesirable data (Table 13-4).