This word refers to personal experiences, self-reported claims,[3] or eyewitness accounts of others,[5] including those from fictional sources, making it a broad category that can lead to confusion due to its varied interpretations.
[2] However, the use of anecdotal reports in advertising or promotion of a product, service, or idea may be considered a testimonial, which is highly regulated in some jurisdictions.
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.
For instance, in medicine, published anecdotal evidence by a trained observer (a doctor) is called a case report, and is subjected to formal peer review.
[21] Although such evidence is not seen as conclusive, researchers may sometimes regard it as an invitation to more rigorous scientific study of the phenomenon in question.
[22] For instance, one study found that 35 of 47 anecdotal reports of drug side-effects were later sustained as "clearly correct.
[27] In any case where some factor affects the probability of an outcome, rather than uniquely determining it, selected individual cases prove nothing; e.g. "my grandfather smoked two packs a day until he died at 90" and "my sister never smoked but died of lung cancer".