You are conducting a study to assess a new fecal occult blood test for colorectal cancer. There are 277 people ages 50-74 in your study. A total of 206 people test negative. Seven people have the disease and test positive. 257 people don't have colorectal cancer and 193 of them test negative. A patient has a positive screen, what is the probability that the patient has colorectal cancer?
A) 93.7%
B) 9.9%
C) 75.1%
D) 35%

Question

Quizplus · Accepted Answer

The probability of having colorectal cancer given a positive screen is the number of people who have the disease and test positive divided by the total number of people who test positive. In this case, 7 people have the disease and test positive, and 206 people test negative. So the probability of having colorectal cancer given a positive screen is 7 / (7 + 206) = 0.099, or 9.9%.

You Are Conducting a Study to Assess a New Fecal