Diagnostic tests of medical situations can have several kinds of results. The test result can be positive or negative, whether or not a patient has condition. A positive test (+) points out that the patient has the condition. A negative test (-) indicates that the patient doesn't have the condition. Remember, a positive test doesn't prove that the patient has the condition. Additional medical work may be needed. Consider random sample of 200 patients, some of whom have medical condition and some of whom don't. Results of a new diagnostic test for condition are shown:
Test Result+ Condition Present 110 Condition Absent 20 Row Total 130
Test Result - Condition PResent 20 Condition Absent 50 Row Total 70
Column Total Condition PResent 130 Condition Absent 70 Row total 200
Suppose the sample is representative of overall population. For a person chosen at radom, calculate the following probabilities:
(a) P(+I condition present); this is known as sensitivity test
(b) P(-I condition present); this is known as false-negative rate
(c) P(-I condition absent); this is known as specificity of a test
(d) P(+1) condition absent); this is known as false-positive rate
(e) P (condition present and +); this is known as predictive value of the test
(f) P(condition present and -);