Anecdotal Evidence

The expression anecdotal evidence refers to evidence from anecdotes. Because of the small sample, there is a larger chance that it may be unreliable due to cherry-picked or otherwise non-representative samples of typical cases. Anecdotal evidence is considered dubious support of a claim; it is accepted only in lieu of more solid evidence. This is true regardless of the veracity of individual claims.

The term is often used in contrast to scientific evidence, such as evidence-based medicine, which are types of formal accounts. Some anecdotal evidence does not qualify as scientific evidence because its nature prevents it from being investigated using the scientific method. Misuse of anecdotal evidence is an informal fallacy and is sometimes referred to as the "person who" fallacy ("I know a person who..."; "I know of a case where..." etc. Compare with hasty generalization). Anecdotal evidence is not necessarily representative of a "typical" experience; in fact, human cognitive biases such as confirmation bias mean that exceptional or confirmatory anecdotes are much more likely to be remembered. Accurate determination of whether an anecdote is "typical" requires statistical evidence.

Accounts of direct personal experience are commonly equated to anecdotal evidence where the evidence is anecdote, hearsay or represents a conclusion deduced from generalisation. Unlike anecdotal evidence, the reliability of accounts of personal experience is normally capable of assessment for legal proceedings.

When used in advertising or promotion of a product, service, or idea, anecdotal reports are often called a testimonial, which are banned in some jurisdictions. The term is also sometimes used in a legal context to describe certain kinds of testimony. Psychologists have found that people are more likely to remember notable examples than typical examples.