The National Center for Statistics and Analysis (NCSA) of the National Highway Traffic Safety Administration (NHTSA) has undertaken several approaches to remedy the problem of missing blood alcohol test results in the Fatality Analysis Reporting System (FARS). The current approach employs a linear discriminant model that estimates the probability that a driver or nonoccupant has a BAC in grams per deciliter (g/dl) of 0, .01 to .09 or .010 and greater. Estimates are generated only for drivers and nonoccupants (pedestrians, pedalcyclists) for whom alcohol test results were not reported. Beginning with the 2001 data, NHTSA will transition to Multiple Imputation, a new method to estimate missing BAC in FARS. The publications for the 2001 data will reflect the estimates of alcohol involvement generated using Multiple Imputation. The new methodology improves on the current model by imputing specific values of BAC across the full range of possible values rather than estimating probabilities. Imputing ten values of BAC for each missing value will permit the estimation of valid statistics such as variances, measures of central tendency, confidence intervals and standard deviations. (A)
Abstract