You are examined by an excellent screening test sensitivity

You are examined by an excellent screening test (sensitivity and specificity of 99%) for a rare disease (0.1% or 1/1000 of the population). Unfortunately, the test is positive. What is the probability that you have the disease?

Solution

First prepare table as follows:

If test is positive, prob that you have disease = The intersection of positive and no disease

= 1%(99.9%)

= 0.0999