From anecdotal evidence

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 statisticalevidence. 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.*