5.89 Screening for colorectal cancer Gigerenzer (2002, p. 105) reported that on the average, “Thirty out of every 10,000 people have colorectal cancer. Of these 30 people with colorectal cancer, 15 will have a positive hemoccult test. Of the remaining 9,970 people without colorectal cancer, 300 will still have a positive hemoccult test.”

a. Sketch a tree diagram or construct a contingency table to display the counts.

b. Of the 315 people mentioned who have a positive hemoccult test, what proportion actually have colorectal cancer? Interpret.