What is Survivor Bias?
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Its the notion that basing statistics on only the observable results from samples that passed some screening or “success” criteria will lead to skewed results and incorrect interpretations.
For example, a study that examines corporate performance of companies who have been in business longer than 10 years – but only examining those companies who are still in business. You should also examine the companies who _were_ in business longer than 10 years but currently are NOT in business. If they were so successful why are they not _still_ in business?
Or, the classic example – in determining where to put extra armor on airplanes, designers looked at where the holes from enemy shells were on the planes that came back to base. But obviously, the ones that made it back to base with bullet holes clearly survived – therefore the bullet hole locations in THOSE planes are not where they needed additional protection – the survivors survived anyway. Its where there were NO bullet holes in the survivors, that’s where the additional protection was needed – clearly planes that got hit in those locations are the ones that didn’t make it.
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