2.4.31. medical records show that 0.01% of the general adult population not belonging to a high-risk group (for example, intravenous drug users) are hiv-positive. blood tests for the virus are 99.9% accurate when given to someone infected and 99.99% accurate when given to someone not infected. what is the probability that a random adult not in a highrisk group will test positive for the hiv virus? larsen, richard j.. an introduction to mathematical statistics and its applications (p. 44). pearson education. kindle edition.