Anecdotal evidence is evidence from anecdotes, i.e., evidence collected in a casual or informal manner and relying heavily or entirely on personal testimony. When compared to other types of evidence, anecdotal evidence is generally regarded as of limited value to a number of potential weaknesses. Anecdotal evidence is sometimes considered within the scope of scientific method. For example the use of case studies in medicine rely on anecdotal evidence, because some anecdotal evidence can be both empirical and verifiable. However, other anecdotal evidence does not qualify as scientific evidence because its nature prevents it from being investigated using the scientific method. 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. Similarly, psychologists have found that due to cognitive bias people are more likely to remember notable or unusual examples rather than typical examples. Thus, even when accurate anecdotal evidence is not necessarily representative of a typical experience. Accurate determination of whether an anecdote is "typical" requires statistical evidence. 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.) which places undue weight on experiences of close peers which may not be typical. Compare with hasty generalization. The term is sometimes used in a legal context to describe certain kinds of testimony which are uncorroborated by objective, independent evidence such as notarized documentation, photographs, audio-visual recordings, etc. 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.

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