Some survey techniques for sampling rare subjects

We have defined a methodology to draw a representative sample that includes the maximum number of respondents with a rare trait when some prior information is available. The method also provides a useful way of incorporating subjective judgement and uncertainty into the sampling plan. This methodology produced very satisfactory results for a rare event problem in telecommunications involving a survey of current non-subscribers of 800-service who would have some application for this service. The proposed method was compared to a range of methods. No clearly dominant technique emerged. Rather, there is a range of population and model parameters for which the proposed method is preferable to the others for studying rare subjects. This is particularly true for the case where small samples are gathered from populations for which abundant, fairly accurate information is available. The method has the advantage of being parsimonious while efficiently using all the available information, quantitative or subjective.