An investigative bureau uses a laboratory method to match the lead in a bullet found at a crime scene with unexpended lead cartridges found in the possession of a suspect. the value of this evidence depends on the chance of a false positivelong dashthat is, the probability that the bureau finds a match, given that the lead at the crime scene and the lead in the possession of the suspect are actually from two different "melts," or sources. to estimate the false positive rate, the bureau collected 1 comma 831 bullets that the agency was confident all came from different melts. then, using its established criteria, the bureau examined every possible pair of bullets and found 678 matches. use this information to compute the chance of a false positive.