Medical Testing in Brief

Overview 

With respect to medical testing in general, the prevalence of a condition in the population has a huge effect on the number of false alarms and misses. Depending on the prevalence of the condition, and the performance of the test, the number of false alarms can exceed the number of hits. It is simple arithmetic, but a bit confusing. 

This is true even with a test of high sensitivity (detects infections if infection exists, with not too many misses) and high selectivity (detection of no infection if no infection exists, with not too many false alarms). 

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