The effect of interviewer variance on domain comparisons - ARCHIVED

In this paper we explore the effect of interviewer variability on the precision of estimated contrasts between domain means. In the first part we develop a correlated components of variance model to identify the factors that determine the size of the effect. This has implications for sample design and for interviewer training. In the second part we report on an empirical study using data from a large multi-stage survey on dental health. Gender of respondent and ethnic affiliation are used to establish two sets of domains for the comparisons. Overall interviewer and cluster effects make little difference to the variance of male/female comparisons, but there is noticeable increase in the variance of some contrasts between the two ethnic groupings used in this study. Indeed, the impact of interviewer effects for the ethnic comparision is two or three times higher than it is for gender contrasts. These findings have particular relevance for health surveys where it is common to use a small cadre of highly-trained interviewers.