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Can someone help explain this question? Please show all your work. The proportio

ID: 3208280 • Letter: C

Question

Can someone help explain this question? Please show all your work.

The proportion of men in the population who have prostate cancer is 35 per 100,000. In 1980, a new test was developed to test for the presence of prostate cancer. The researchers who developed the test wanted to know the probability that a man who tested positive for prostate cancer actually had the disease. To find this probability, they took a random sample of 99 men known to have prostate cancer and another random sample of 150 men known not to have prostate cancer (after having a biopsy). Their test is a radioimmunoassay for prostate acid phosphatase (RIA-PAP). They found the following results (real data). Let C = a randomly selected man has prostate cancer Use 3 decimal places. P(C | Pos) = 0.398 P(C^c | Pos) =

Explanation / Answer

Let's use the letters And B to denote the following:

A : number of people who have a cancer and tested positive

B : number of people who don't have a cancer but still tested positive

From the table given above, we see:

A = 69

B = 11

So,

P(C | Pos) = A / (A+B) = 69/(69+11) = 0.8625

P(Cc | Pos) = 1 - P(C | Pos) = 0.1375