Frank and Chris both took the ABC achievement test, which is N(950,50). If frank had a z-score of 2.5 and Chris had a score of 675, how much higher was Frank's score?
1075
1700
400
525
none of the above

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)