Survey: Medical Tests 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 that 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.

Condition Present Condition Absent Row Total Test Result + 110 20 130 Test Result − 20 50 70 Column Total 130 70 200 Assume the sample is representative of the entire population. For a person selected at random, compute the following probabilities:

(a) P 1( |condition present); this is known as the sensitivity of a test.

(b) P 2( |condition present); this is known as the falsenegative rate.

(c) P 2( | condition absent); this is known as the specificity of a test.

(d) P 1( | condition absent); this is known as the falsepositive rate.

(e) P(condition present and 1); this is the predictive value of the test.

(f) P(condition present and 2).

AppendixLO1