False Positive / False Negative

 

These are two important phrases used in many areas of computer science and other sciences. Long time back I had trouble understanding them. This is an attempt at writing them to down to ensure I can describe it to others.

False Positive: When some test says you have cancer when in reality you don’t then the test is exhibiting false positive. It is giving a positive test response to a non-existent decease.

False Negative:When a test is saying you don’t have cancer when you do have cancer is exhibiting false negative. False negative results are really bad in medical testing as they give false sense of security for the patient.

In practice when dealing with large sample size False Positive tests are fine as long as the false negative rate is very very low. A test with reasonable false positive rates can reduce the sample size to a very small size which can be fed to a more thorough test that can establish the presence of the decease.

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