Public Opinion Quarterly Advance Access originally published online on February 1, 2008
Public Opinion Quarterly 2008 72(1):28-39; doi:10.1093/poq/nfn001
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A "Brute Force" Estimation of the Residency Rate for Undetermined Telephone Numbers in an RDD Survey
Address correspondence to Courtney Kennedy; e-mail: ckkenned{at}umich.edu.
In random digit dial (RDD) telephone surveys, some proportion of the sampled telephone numbers cannot definitively be classified as eligible or ineligible. Each call attempt to these numbers generally results in either a busy signal or a ring with no answer. According to the profession's standard definitions, the proportion of these unresolved numbers that are, in fact, eligible is known as "e" and should be accounted for in response rate calculations. We used call records and a directory listed indicator from a survey with an extended calling period (and other features – letters, incentives, etc.) to resolve as many unknown cases as possible and thus derive an empirical estimate (.47) for "e." We found additional support for this estimate by matching the unresolved telephone numbers from a separate survey to residency information from a commercial data vendor. The estimate of "e" applies to national RDD surveys featuring approximately a six-call design.
COURTNEY KENNEDY is with the University of Michigan, Program in Survey Methodology, 426 Thompson Street, Room 4050, Ann Arbor, MI 48104, USA. SCOTT KEETER AND MICHAEL DIMOCK are with The Pew Research Center for the People & the Press 1615 L Street, NW Suite 700 Washington, DC 20036, USA. We thank the anonymous reviewers and J. Michael Brick for their helpful advice.