A coin-operated machine sells plastic rings. It contains 6 yellow rings, 11 blue rings, 15 green rings, and 3 black rings. Sarah puts a coin into the machine. Find the theoretical probability she gets a black ring. Express your answer as a decimal. If necessary, round your answer to the nearest thousandth. A.11.667
B.0.171
C.5.833
D.0.086

Anew test for ra is being developed. the test is administered to 750 patients with ra and 750 without ra. for the sake of the question, assume the prevalence of ra in this population is 50%. of the 750 patients with ra, 575 have a positive result. of the 750 patients without ra, 150 have a positive result. what is the positive predictive value of the new test? a575/(575+150) b. 600/(600+ 150) c. 575/(575+125) d. 600/(600+ 125)