Common Reasoning Mistakes - Health Policy

Confirmation bias

Favoring evidence that supports a belief we already hold

Motivated reasoning

Letting a desired conclusion steer how we search for and evaluate evidence

Selecting on the dependent variable

Examining only people with an outcome, then treating their traits as its explanation

Anecdotal overweighting

Allowing a vivid anecdote to outweigh more representative outcome evidence

Base-rate neglect

Ignoring how common an outcome is before interpreting a test or a symptom

Denominatory neglect

Focusing on the number of bad outcomes while overlooking the population

Relative vs absolute risk

Interpreting a proportional reduction as if it were a percentage-point reduction

Small samples

Treating a result from a few observations as a stable estimate of population risk

Post hoc reasoning

Assuming that because an outcome followed an event, the event caused it

Overlooked selection

attributing group differences to treatment when the groups differ in other relative ways

Reverse causation

Mistaking a consequence of illness for a cause of later poor health

Regression to the mean

Attributing a return from an extreme measurement entirely to an intervention

Anchoring

Giving an initial label too much weight and adjusting too little to other evidence

Framing

Changing a judgement when equivalent outcomes are described in different ways

Overconfidence

Expressing more certainty than the accuracy or strength of evidence warrants

Omission bias

Judging harm from inaction more leniently than comparable harm from action