a prostate specific antigen (psa) test is a quick screening test for prostate cancer. a researcher wants to evaluate it using two groups. group a consists of 2,500 men who had biopsy-proven adenocarcinoma of the prostate while group b consists of 4,000 age- and race-matched men all of whom showed no cancer at biopsy. the results of the psa screening test in each group is shown in the table. group a group b positive for psa screening test 1,975 370 total in group 2,500 4,000 what is the positive predictive value of the screening test in this population? 94% 79% 84% 87%