What is "anecdotal evidence"

n. A limited selection of examples which support or refute an argument, but which are not supported by scientific or statistical analysis.

Anecdotal evidence is evidence from anecdotes. Where only one or a few anecdotes are presented, there is a larger chance that they may be unreliable due to cherry-picked or otherwise non-representative samples of typical cases. Anecdotal evidence is considered within the scope of scientific method for claims regarding particular instances, for example the use of case studies in medicine because some anecdotal evidence can be both empirical and verifiable, while other 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 as it is a personal testimony; 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.

The term is 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. 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.