Improved imputation of non‐responses to mailback questionnaires

Abstract
Poor response rates, perhaps as low as 10 to 30 per cent, certainly bring into question the validity of any survey suffering such a malady. Repeated mailouts are capable of providing information on those persons who are resistant to responding. If one is willing to assume an exponential drop-off in response rates, then imputation is possible for the entire group of non-responders. Furthermore, a second exponential drop-off in favourable (or non-favourable) responses to particular items within the questionnaire leads to closed form estimates of population parameters and their associated standard errors. Three or more mailouts also provide a test of validity of the model assumed.