Anecdotal evidence

Anecdotal evidence is evidence based only on personal observation, collected in a casual or non-systematic manner. When used in advertising or promotion of a product, service, or idea, anecdotal reports are often called a testimonial, which are highly regulated in some jurisdictions.^[1]

Anecdotal evidence may be considered within the scope of scientific method as some anecdotal evidence can be both empirical and verifiable, e.g. in the use of case studies in medicine. Other anecdotal evidence, however, does not qualify as scientific evidence, because its nature prevents it from being investigated by the scientific method, for instance, in that of folklore or in the case of intentionally fictional anecdotes. Where only one or a few anecdotes are presented, there is a chance that they may be unreliable due to cherry-picked or otherwise non-representative samples of typical cases.^[2][3] Similarly, psychologists have found that due to cognitive bias people are more likely to remember notable or unusual examples rather than typical examples.^[4] 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.^[5] Misuse of anecdotal evidence in the form of argument from anecdote is an informal fallacy^[6] 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.