Quality & Quantity 36: 129–144, 2002.
© 2002 Kluwer Academic Publishers. Printed in the Netherlands.
The Importance of Experimental Control in Testing
the Impact of Interviewer Continuity on Panel
and COLM O’MUIRCHEARTAIGH
Independent Survey Research Consultant, 33 Military Road, Colchester, Essex C01 2AD, U.K.;
University of Chicago, U.S.A.
Abstract. The conventional wisdom in survey research suggests that it is advisable to have the same
interviewers return to the same respondents in order to maintain good response rates in longitudinal
surveys. There has been, however, very little documented experimental research to support this. Work
conducted by Campanelli and O’Muircheartaigh (1999) using a subsample of the British Household
Panel Study (BHPS) at Wave 2 with experimental control of the allocation of respondents to inter-
viewers showed no evidence of a positive continuity effect on nonresponse; more extensive analysis
by Laurie et al. (1999) of the full BHPS sample using Waves 2 through 4 presents contradictory
results. This paper extends the earlier analysis and shows that these differences in ﬁndings are due
to the lack of experimental control for the inferences from the full BHPS sample in the Laurie et
al. (1999) report rather than the shorter time frame considered in Campanelli and O’Muircheartaigh
(1999). This paper also considers variation in interviewer continuity effects across areas through the
use of multilevel statistical models.
Key words: interviewers, panel surveys, nonresponse, interviewer continuity, hierarchical models.
1. The Issue of Interviewer Continuity
Sending the same interviewers back to the same respondents at later waves of
data collection is generally considered advisable in panel study designs. Such
“interviewer continuity” is generally thought to improve response rates mainly
by reducing the refusal component of nonresponse. A possible explanation for
this is the longitudinal rapport which develops between interviewer and respond-
ent. For example, the work of Morton-Williams (1993) suggests that individuals
who are motivated to participate in the survey because of their feelings about
the interviewer and the process of being interviewed could be more sensitive to
a lack of interviewer continuity. Similarly, the work of Groves et al. (1992) suggest
that respondents using “heuristic” decision strategies can base their participation
decisions in the current wave on their experience with a particular interviewer
and/or interview experience from a previous wave. It is also reasonable to assume
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