Neglect of prior base rates effect

The prior base rate effect is a cognitive bias that occurs when people rely too heavily on specific base rates when making decisions instead of taking into account the additional relevant information that may be available. This can lead to incorrect decisions that are less accurate than if all relevant information had been taken into account. Specifically, the base rate refers to the inherent probability of an event occurring under certain conditions; for example, the base rate of a disease may be the probability of someone having it in the absence of any tests or other indicators. Neglecting the prior base rates can lead to incorrect assumptions about outcomes when additional information is taken into account. For example, if a person is tested for a disease and receives a positive result, the base rate of the disease may be lower than the test result suggests. If a decision is made only on the basis of the test result, the outcome may be more likely than if the prior base rate was also taken into account.