Question

The probability of a false negative is 0.1%; the probability of a false positive is 10%. The prevalence of the disease in the population is 2%. Given a person tests positive, what is the probability that (s)he does nothave the disease?

Answer 1

From the given daa, the following Table is calculated:

	Have disease	Do not have disease	Total
Test positive	0.019	0.100	0.119
Test negative	0.001	0.98 - 0.100=0.88	0.881
Total	0.02	1 - 0.02 = 0.98	1.00

P(Do not have disease/ Test positive) = P(Do not have disease AND Test positive)/ P(Test positive)

                                                       = 0.100/0.119 = 0.8403

So,

Answer is:

0.8483