A STATISTICAL-MODEL FOR THE RESPONSE PATTERNS TO CHEMICAL-TESTS FOR THE ABSENCE OR PRESENCE OF TRACE MATERIALS

A statistical method is described which enables comparisons to be made between two sets of data where each datum can only be expressed as a positive or negative value. The method is based upon logistic regressi on analysis. It has been applied to patterns of positive and negative responses to chromatographic analyses carried out on hand swabs taken from a number of subjects suspected of handling explosives, and experi mentally simulated data acquired on the basis of a contamination hypot hesis. The analyses indicate that both patterns demonstrate ordering a nd that these orders are statistically indistinguishable.