Optimal Survey Design When Nonrespondents are Subsampled for Followup

A. James O’Malley
Harvard Medical School

Healthcare surveys often first mail questionnaires to sampled members of health plans and then follow up mail nonrespondents by phone. The high unit costs of telephone interviews make it cost-effective to subsample the followup. We derive optimal subsampling rates for the phone subsample for comparison of health plans. Computations under design-based inference depart from the traditional formulae for Neyman allocation because the phone sample size at each plan is constrained by the number of mail non-respondents and multiple plans are subject to a single cost constraint. Because plan means for mail respondents are highly correlated with those for phone respondents, more precise estimates (at fixed overall cost) for potential phone respondents are obtained by combining the direct estimates from phone followup with predictions from the mail survey using small-area estimation (SAE) models.

Session 2a, Sample Surveys: 11:30 — 11:50, Room 031

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