Problem 8 A prevalence base line of TMX disease is 07 A scre

Problem 8. A prevalence (base line) of TMX disease is 0.7%. A screening test for a TMX disease has 6% false positive rate and 11% false negative rate. If a person is negative on the test what is a probability that he is really healthy.

Solution

Consider the table:

Thus,

P(actual negative|test negative) = P(actual negative and test negative) / P(test negative) = 0.93742 / (0.93742+0.00077)

= 0.999179271 or 99.918% [ANSWER]

	Test Positive	Test Negative
Actual Positive	0.00623	0.00077
Actual Negative	0.05958	0.93742