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 above who have a positive hemoccult test, what proportion actually have colorectal cancer? Interpret.