ESTIMATION OF NON-RESPONDENT BAC USING A PRIORI JUDGMENT

Two methods of adjusting for non-participation bias in roadside breath testing surveys are compared. Method 1 uses the assumption that the probability of measured BAC level conditional on a priori judgement of drinking is the same for respondents and nonrespondents. Method 2 uses the assumption that the probability of a priori judgement of drinking conditional on BAC level is the same for respondents and nonrespondents. Method 2 yields substantially larger estimated probabilities of high BAC for nonrespondents. Both methods can be supported by sound logical arguments. Method 2 is shown to yield negative probabilities, when applied to a large roadside survey sample, and is thereby rejected. © 1979.