In a study of 250 adults, the average heart rate was 70 beats per minute. Assume the population of heart rates is known to be approximately normal, with a standard deviation of 12 beats per minute. What does a margin of error of 2 for the 98% confidence interval of the average beats per minute mean?

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)