A disease affects one person in every thousand. A medical test for this disease is 99 percent accurate, meaning it correctly identifies 99 percent of sick people and correctly clears 99 percent of healthy people. You take the test and the result is positive. What is the probability that you actually have the disease? Most people, including a substantial fraction of medical professionals when this problem is presented to them, answer something in the range of 99 percent. The correct answer is approximately 9 percent. If you find this result shocking, you have just encountered the base rate neglect problem,...