Explain what a false positive and a false negative are.

Provide examples when false positives are more important than false negatives, false negatives are more important than false positives and when these two types of errors are equally important.

False positive

Improperly reporting the presence of a condition when it's not in reality. Example: HIV positive test when the patient is actually HIV negative.

False negative

Improperly reporting the absence of a condition when in reality it's the case. Example: not detecting a disease when the patient has this disease.

When false positives are more important than false negatives:



  • In a non-contagious disease, where treatment delay doesn't have any long-term consequences but the treatment itself is grueling.
  • HIV test: psychological impact.


When false negatives are more important than false positives:


  1. If early treatment is important for good outcomes.
  2. In quality control: a defective item passes through the cracks!
  3. Software testing: a test to catch a virus has failed.

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