Interviewer Variance

Interviewer variance describes the part of the overall variability in a survey statistic that is associated with the interviewer. Clusters of respondents interviewed by the same person tend to have more similar responses than do clusters of respondents interviewed by different interviewers. This cluster effect can appear, for example, if an interviewer uses inappropriate or inconsistent probing techniques, has idiosyncratic interpretations of questions and rewords them accordingly, or differs in the way he or she reads answer categories. In addition, interviewer-specific interactions between the interviewer and respondent can lead to an intra-interviewer covariance term that contributes to the variance of the estimate.

The effect of interviewers on responses can increase the variability of survey estimates in a way parallel to the effect of clustered samples. The ...