Diagnostic tests of medical conditions can have several types of results. The te
ID: 3062845 • Letter: D
Question
Diagnostic tests of medical conditions can have several types of results. The test result can be positive or negative, whether or not a patient has the condition. A positive test (+) indicates that the patient has the condition. A negative test () indicates that the patient does not have the condition. Remember, a positive test does not prove the patient has the condition. Additional medical work may be required. Consider a random sample of 200 patients, some of whom have a medical condition and some of whom do not. Results of a new diagnostic test for the condition are shown.
(a) P(+ | condition present); this is known as the sensitivity of a test.
(b) P( | condition present); this is known as the false-negative rate.
(c) P( | condition absent); this is known as the specificity of a test.
(d) P(+ | condition absent); this is known as the false-positive rate.
(e) P(condition present and +); this is the predictive value of the test.
(f) P(condition present and ).
Explanation / Answer
a) P(+ | condition present)=101/119=0.8487
b) P( | condition present) =18/119 =0.1513
c) P( | condition absent)=52/81=0.6420
d)P(+ | condition absent) =29/81=0.3580
e) P(condition present and +) =101/200 =0.505
f) P(condition present and ) =18/200=0.09