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Encyclopedia > Anecdotal evidence

Anecdotal evidence is an informal account of evidence in the form of an anecdote, or hearsay. The term is usually used in contrast to scientific evidence, especially evidence-based medicine, which are types of formal accounts. Anecdotal evidence is often unscientific because it cannot be investigated using the scientific method. Misuse of anecdotal evidence is a logical fallacy and is sometimes informally referred to as the "person who" fallacy ("I know a person who..."; "I know of a case where..." etc.) The problem with arguing based on anecdotal evidence is that anecdotal evidence is not necessarily typical; only statistical evidence can determine how typical something is. Evidence has several meanings as indicated below. ... An anecdote is a brief tale narrating an interesting or amusing biographical incident. ... Hearsay in its most general and oldest meaning is a term used in the law of evidence to describe an out of court statement offered to establish the facts asserted in that statement. ... The scientific method or process is fundamental to the scientific investigation and acquisition of new knowledge based upon physical evidence. ... Evidence-based medicine (EBM) applies the scientific method to medical practice. ... Scientific method refers to a body of techniques for the investigation of phenomena and the acquisition of new knowledge of the natural world, as well as the correction and integration of previous knowledge, based on observable, empirical, measurable evidence, and subject to laws of reasoning. ... In philosophy, the term logical fallacy properly refers to a formal fallacy: a flaw in the structure of a deductive argument which renders the argument invalid. ... For Wikipedia statistics, see m:Statistics Statistics is the science and practice of developing human knowledge through the use of empirical data expressed in quantitative form. ...

When used in advertising or promotion of a product, service, or idea, anecdotal evidence is often called a testimonial. The term is also 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 the typical example. This is why casinos usually try to draw attention to someone winning; this tends to make everyone else think that they are much more likely to win than they are. Another example is the fact that people are often afraid to fly after a major airline accident, even though flying is statistically similar in risk to driving. Advertising, generally speaking, is the promotion of goods, services, companies and ideas, usually performed by an identified sponsor. ... Testimonial - Wikipedia /**/ @import /skins-1. ... In law and in religion, testimony is a solemn attestation as to the truth of a matter. ... For other uses, see Casino (disambiguation). ...

What constitutes anecdotal evidence is sometimes disputed on scientific or philosophical grounds. For mathematical sciences, see mathematics. ... Philosopher in Meditation (detail), by Rembrandt. ...



In all forms of anecdotal evidence, testing its reliability by objective independent assessment may be in doubt. This is a consequence of the informal way the information is gathered, documented, presented, or any combination of the three. The term is often used to describe evidence for which there is an absence of documentation. This leaves verification dependent on the credibility of the party presenting the evidence.

Scientific context

In science, anecdotal evidence has been defined as:

  • "information that is not based on facts or careful study" [1]
  • "non-scientific observations or studies, which do not provide proof but may assist research efforts" [2]
  • "reports or observations of usually unscientific observers" [3]
  • "casual observations or indications rather than rigorous or scientific analysis" [4]
  • "information passed along by word-of-mouth but not documented scientifically"

Anecdotal evidence can have varying degrees of formality. For instance, in medicine, published anecdotal evidence is called a case report, which is a more formalized type of evidence subjected to peer review. [5] Although such evidence is not regarded as scientific, it is sometimes regarded as an invitation to more rigorous scientific study of the phenomenon in question. [6] For instance, one study found that 35 of 47 anecdotal reports of side effects were later sustained as “clearly correct.” [7] In medicine, a case report is a detailed report of the diagnosis, treatment, and follow-up of an individual patient. ... Peer review (known as refereeing in some academic fields) is a scholarly process used in the publication of manuscripts and in the awarding of funding for research. ...

Researchers may use anecdotal evidence for suggesting new hypotheses, but never as supporting evidence. A hypothesis is a suggested explanation of a phenomenon or reasoned proposal suggesting a possible correlation between multiple phenomena. ...

Anecdotal evidence and faulty logic

Anecdotal evidence is often unscientific or pseudoscientific because various forms of cognitive bias may affect the collection or presentation of evidence. For instance, someone who claims to have had an encounter with a supernatural being or alien may present a very vivid story, but this is not falsifiable. This phenomenon can also happen to large groups of people through subjective validation. Phrenology is regarded today as being a classic example of pseudoscience. ... Cognitive bias is any of a wide range of observer effects identified in cognitive science and social psychology including very basic statistical, social attribution, and memory errors that are common to all human beings. ... In science and the philosophy of science, falsifiability, contingency, and defeasibility are roughly equivalent terms referring to the property of empirical statements that they must admit of logical counterexamples. ... The Forer effect (also called personal validation fallacy or the Barnum effect after P. T. Barnum) is the observation that individuals will give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them, but are in fact vague and general enough to apply to a...

Anecdotal evidence is also frequently misinterpreted via the availability heuristic, which leads to an overestimation of prevalence. Where a cause can be easily linked to an effect, people overestimate the likelihood of that the cause does have that effect (availability). In particular, vivid, emotionally-charged anecdotes seem more plausible, and are given greater weight. A related issue is that it is usually impossible to assess for every piece of anecdotal evidence, the rate of people not reporting that anecdotal evidence in the population. It has been suggested that Availability error be merged into this article or section. ...

A common way anecdotal evidence becomes unscientific is through fallacious reasoning such as the post hoc fallacy, the human tendency to assume that if one event happens after another, then the first must be the cause of the second. Another fallacy involves inductive reasoning. For instance, if an anecdote illustrates a desired conclusion rather than a logical conclusion, it is considered a faulty or hasty generalization. [8] For example, here is anecdotal evidence presented as proof of a desired conclusion: A fallacy is a component of an argument that is demonstrably flawed in its logic or form, thus rendering the argument invalid (except in the case of begging the question) in whole. ... Post hoc ergo propter hoc is Latin for after this, therefore because of this. ... // Induction or inductive reasoning, sometimes called inductive logic, is the process of reasoning in which the premises of an argument support the conclusion but do not ensure it. ... A faulty generalization, also known as an inductive fallacy, is any of several errors of inductive inference: Hasty generalization is the fallacy of examining just one or very few examples or studying a single case, and generalizing that to be representative of the whole class of objects or phenomena. ... Hasty generalization, also known as fallacy of insufficient statistics, fallacy of insufficient sample, fallacy of the lonely fact, leaping to a conclusion, hasty induction, law of small numbers, unrepresentative sample or secundum quid, is the logical fallacy of reaching an inductive generalization based on too little evidence. ...

"There's abundant proof that God exists and is still performing miracles today. Just last week I read about a girl who was dying of cancer. Her whole family went to church and prayed for her, and she was cured."

Anecdotes like this are very powerful persuaders, but they don't prove anything in a scientific or logical sense. [9] The child may have become better anyway and this could be an example also of the regressive fallacy. Anecdotal evidence cannot be distinguished from placebo effects. [10] Only double-blind randomized placebo-controlled clinical trials can confirm a hypothesis. The regression (or regressive) fallacy is a logical fallacy where regression towards the mean is seen not as a natural fluctuation but as being brought about by a specific cause. ... The placebo effect (Latin placebo, I shall please), first mentioned in 1955 by Henry K. Beecher, M.D. [1] and also known as non-specific effects and the subject-expectancy effect, is the phenomenon that a patients symptoms can be alleviated by an otherwise ineffective treatment, since the individual... Double-blind describes an especially stringent way of conducting an experiment, usually on living, conscious, human subjects. ... This article is in need of attention from an expert on the subject. ... A placebo, from the Latin for I will please, is a medical treatment (operation, therapy, chemical solution, pill, etc. ... In medicine, a clinical trial (synonyms: clinical studies, research protocols, medical research) is a research study. ... A hypothesis is a suggested explanation of a phenomenon or reasoned proposal suggesting a possible correlation between multiple phenomena. ...

Sites devoted to rhetoric [11] often give explanations along these lines: Rhetoric from Greek ρήτωρ, rhêtôr, orator) is the art or technique of persuasion, usually through the use of language. ...

Anecdotal evidence, for example, is by definition less statistically reliable than other sorts of evidence, and explanations do not carry the weight of authority. But both anecdotal evidence and explanations may affect our understanding of a premise, and therefore influence our judgment. The relative strength of an explanation or an anecdote is usually a function of its clarity and applicability to the premise it is supporting. [1]

By contrast, in science and logic, the "relative strength of an explanation" is based upon its ability to be tested, proven to be due to the stated cause, and verified under neutral conditions in a manner that other researchers will agree has been performed competently, and can check for themselves.


Witness testimony is a common form of evidence in law, and law has mechanisms to test witness evidence for reliability or credibility. Legal processes for the taking and assessment of evidence are formalized. Some witness testimony could be described as anecdotal evidence, such as individual stories of harassment as part of a class action lawsuit. However, witness testimony can be tested and assessed for reliability. Examples of approaches to testing and assessment include the use of questioning, evidence of corroborating witnesses, documents, video and forensic evidence. Where a court lacks suitable means to test and assess testimony of a particular witness, such as the absence of forms of corroboration or substantiation it may afford that testimony limited or no "weight" when making a decision on the facts. This article is about witnesses in law courts. ... In law and in religion, testimony is a solemn attestation as to the truth of a matter. ... The law of evidence governs the use of testimony (e. ... Harassment refers to a wide spectrum of offensive behavior. ... In law, a class action is an equitable procedural device used in litigation for determining the rights of and remedies, if any, for large numbers of people whose cases involve common questions of law and fact. ...

Scientific evidence as legal evidence

In certain situations, scientific evidence presented in court must also meet the legal requirements for evidence. For instance, in the United States, expert testimony of witnesses must meet the Daubert Standard. This ruling holds that before evidence is presented to witnesses by experts, the methodology must be "generally accepted" among scientists. In some situations, anecdotal evidence may meet this threshold (such as certain case reports which corroborate or refute other evidence). The Daubert Standard is a legal precedent set in 1993 by the Supreme Court of the United States regarding the admissibility of expert witnesses testimony during legal proceedings. ...

Miller and Miller (2005) list five standards of proof, by level of evidence [12]:

Kind Level of Evidence Standard
Regulatory, Legal Precautionary Principle
Legal - Civil * More likely than not
Legal - Civil ** Clear and convincing
Legal - Criminal *** Beyond a reasonable doubt
Scientific **** Irrefutable

Citing situations involving adverse drug reactions, Miller and Miller outline three events related to administration of the drug which can prove specific causation:

  • challenge: the reaction occurs after the drug is given
  • de-challenge: it resolves when the drug is discontinued
  • re-challenge: the adverse event recurs when the drug is given a second time. (Cook County 2005)

Altman and Bland argue that the case report or statistical outlier cannot be dismissed as having no weight: "With rare and uncommonly occurring diseases, a nonsignificant finding in a randomized trial does not necessarily mean that there is no causal association between the agent in question and the disease." [13]

Miller and Miller conclude: "Most medical evidence does not meet the scientific standard of proof; and, as in law, it should be judged by a standard of proof appropriate to the fact or point in question. An 'anecdotal' case report can provide evidence of probative value, just like eyewitness testimony in a murder trial. And it can be similarly tested, by second opinions, re-examination, laboratory tests, and follow-up."[12]


  1. ^ Cambridge Advanced Learner's Diuctionary
  2. ^ Dictionary.com
  3. ^ Merriam-Webster
  4. ^ YourDictionary.com
  5. ^ Jenicek M. "Clinical Case Reporting" in Evidence-Based Medicine. Oxford: Butterworth–Heinemann; 1999:117
  6. ^ Vandenbroucke JP (2001). In Defense of Case Reports and Case Series. Annals of Internal Medicine. Vol. 134:4, 300-334
  7. ^ Venning GR. Validity of anecdotal reports of suspected adverse drug reactions: the problem of false alarms. Br Med J (Clin Res Ed). 1982;284:249-52.PMID: 0006799125
  8. ^ Thompson B. Fallacies.
  9. ^ Logic via infidels.org
  10. ^ Lee D (2005). Evaluating Medications and Supplement Products. via MedicineNet
  11. ^ Graham R. Anecdotes.
  12. ^ a b Miller, DW Jr, Miller, CG. On evidence, medical and legal. Journal of American Physicians and Surgeons Volume 10 Number 3, Fall 2005, 70-75.
  13. ^ Altman DG, Bland M. Absence of evidence is not evidence of absence. British Medical Journal, 1995;311:485


are you kiddin ? i was lookin for it for hours ... The Santa Rosa Junior College (SRJC) is a community college located in the city of Santa Rosa in Sonoma County, California. ... The Skeptics Dictionary is a web site with a collection of cross-referenced skeptical essays by Robert Todd Carroll, PhD. It primarily exposes claims that its editors consider pseudoscientific (sometimes in a pseudoskeptical fashion though). ...

See also

  Results from FactBites:
Anecdotal evidence - Wikipedia, the free encyclopedia (1335 words)
Anecdotal evidence is an informal account of evidence in the form of an anecdote, or hearsay.
Anecdotal evidence is often unscientific because it cannot be investigated using the scientific method.
Anecdotal evidence is often unscientific or pseudoscientific because various forms of cognitive bias may affect the collection or presentation of evidence.
  More results at FactBites »



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