STATISTICAL-ANALYSIS OF BLOOD-ALCOHOL TO BREATH-ALCOHOL RATIO DATA INTHE LOGARITHM-TRANSFORMED AND NONTRANSFORMED MODES

The statistical analysis of non-transformed and logarithm-transformed blood- to breath-alcohol ratios (''blood/breath ratios'') is detailed. The data analyzed were derived from 137 simultaneous blood-alcohol an d breath-alcohol concentration measurements made between 15 and 179 mi n after the end of drinking, with 136 of the measurements obtained dur ing the 15- to 124-min time frame. Although the distribution of the no n-transformed ratios is positively skewed, and that of the logarithm-t ransformed data more closely approximates the normal distribution upon visual inspection, both analyses generated results that do not differ significantly from each other when considered in the context of ''mea n ratios +/- 2SD''. This is in accord with the results of the Kolmogor ov-Smirnov goodness-of-fit test, which does not reject either dataset and demonstrates that both are approximately normal. Since the logarit hm-transformed data generate more conservative statistical blood/breat h ratio ranges than the non-transformed data, they were selected as th e basis for the principal conclusion of this work. That conclusion is a refutation of the argument that, breath-alcohol analyzers relying on a 2100:1 blood/breath ratio tend to underestimate the blood-alcohol c oncentrations of driving-while-intoxicated arrestees because the commo nly accepted mean postabsorptive ratio is 2300:1. In fact, whenever th e absorption status of a driving-while-intoxicated arrestee at the tim e of a breath test cannot be definitively established, the results of this work support the application of a relative error range of -40% to + 28% for 95% of the population, based on a statistical blood/breath ratio range of 1259:1 to 2679:1, and -46% to + 42% for 99% of the popu lation, based on a statistical range of 1128:1 tp 2989:1.