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The expression anecdotal evidence has two quite distinct meanings.

(1) Evidence in the form of an anecdote or hearsay is called anecdotal if there is doubt about its veracity: the evidence itself is considered untrustworthy or untrue. Evidence in its broadest sense includes anything that is used to determine or demonstrate the Truth of an assertion For other uses see Anecdota. For a comparison of anecdote with other kinds of stories see Myth legend fairy tale and fable. Not to be confused with Heresy. Hearsay is a legal term referring to the use of out of court statements as evidence

(2) Evidence which may itself be true and verifiable is used to deduce a conclusion which does not follow from it, usually by generalising from an insufficient amount of evidence. For example "my grandfather smoked like a chimney and died healthy in a car crash at the age of 99" does not disprove the proposition that "smoking markedly increases the probability of cancer and heart disease at a relatively early age". In this case the evidence may itself be true, but does not warrant the conclusion.

In both cases the conclusion is unreliable; it might happen not to be untrue, but it doesn't follow from the "evidence".

Evidence can be anecdotal in both senses: "Goat yoghurt prolongs life: I heard that a man in a mountain village who ate only yoghurt lived to 120".

The term is often used in contrast to scientific evidence, such as evidence-based medicine, which are types of formal accounts. Scientific evidence is Evidence which serves to either support or counter a scientific Theory or Hypothesis. Evidence-based medicine (EBM aims to apply Evidence gained from the Scientific method to certain parts of medical practice Some anecdotal evidence does not qualify as scientific evidence because its nature prevents it from being investigated using the scientific method. Scientific method refers to bodies of Techniques for investigating phenomena Misuse of anecdotal evidence is a logical fallacy and is sometimes informally referred to as the "person who" fallacy ("I know a person who. A fallacy is a component of an Argument which being demonstrably flawed in its Logic or form renders the argument invalid in whole . . "; "I know of a case where. . . " etc. Compare with hasty generalization). Hasty generalization is a Logical fallacy of Faulty generalization by reaching an inductive Generalization based on insufficient Evidence Anecdotal evidence is not necessarily typical; statistical evidence can more accurately determine how typical something is. Statistics is a mathematical science pertaining to the collection analysis interpretation or explanation and presentation of Data.

When used in advertising or promotion of a product, service, or idea, anecdotal reports are often called a testimonial, banned in some jurisdictions. Advertising is a form of Communication that typically attempts to persuade potential Customers to Purchase or to consume more of a particular Brand For the use of the term testimonial in sport (especially Football) see Testimonial match. The term is also sometimes used in a legal context to describe certain kinds of testimony. "Testify" redirects here For other uses see Testify (disambiguation and Testimony (disambiguation. Psychologists have found that people are more likely to remember notable examples than typical examples[1].

Contents

Introduction

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:

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. In Medicine, a case report is a detailed report of the Symptoms signs Diagnosis, treatment and follow-up of an individual Patient Peer review (also known as refereeing) is the process of subjecting an author's scholarly work research or Ideas to the scrutiny of others who are [6] 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. [7] For instance, one study found that 35 of 47 anecdotal reports of side effects were later sustained as “clearly correct. ” [8]

Researchers may use anecdotal evidence for suggesting new hypotheses, but never as supporting evidence. A hypothesis (from Greek) consists either of a suggested explanation for a phenomenon (an event that is observable or of a reasoned proposal suggesting a possible

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. Pseudoscience is defined as a body of knowledge methodology belief or practice that is claimed to be Scientific or made to appear scientific but does not adhere to the For an article about the conceptual problems of the mind see Cognitive closure (philosophy. 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. Falsifiability (or "refutability" is the logical possibility that an assertion can be shown false by an observation or a physical experiment This phenomenon can also happen to large groups of people through subjective validation. Subjective validation, sometimes called personal validation effect, is a Cognitive bias by which a person will consider a statement or another piece of information

Anecdotal evidence is also frequently misinterpreted via the availability heuristic, which leads to an overestimation of prevalence. The availability heuristic is a phenomenon (which can result in a Cognitive bias) in which people base their prediction of the frequency of an event or the proportion within Where a cause can be easily linked to an effect, people overestimate the likelihood of the cause having 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.

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. A fallacy is a component of an Argument which being demonstrably flawed in its Logic or form renders the argument invalid in whole Post hoc ergo propter hoc, Latin for "after this therefore because (on account of this" is a logical fallacy (of the Questionable cause variety Another fallacy involves inductive reasoning. Induction or inductive reasoning, sometimes called inductive logic, is the process of Reasoning in which the premises of an argument are believed For instance, if an anecdote illustrates a desired conclusion rather than a logical conclusion, it is considered a faulty or hasty generalization. A faulty generalization, also known as an inductive fallacy, is any of several errors of inductive inference: Logic The proportion Q of the sample Hasty generalization is a Logical fallacy of Faulty generalization by reaching an inductive Generalization based on insufficient Evidence [9] For example, here is anecdotal evidence presented as proof of a desired conclusion:

More generally, a statistical correlation between things does not in itself prove that one causes the other (a causal link). Causality (but not causation) denotes a necessary relationship between one event (called cause and another event (called effect) which is the direct consequence A study found that television viewing was strongly correlated with sugar consumption, but this does not prove that viewing causes sugar intake (or viceversa).

"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 do not prove anything. [10] 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 40 a day until he died at 90" and "my sister never went near anyone who smoked but died of lung cancer".

In medicine anecdotal evidence is also subject to placebo effects[11]: it is well-established that a patient's (or doctor's) expectation can genuinely change the outcome of treatment. Placebo is a substance or procedure a patient accepts as medicine or therapy but which has no specific therapeutic activity Only double-blind randomized placebo-controlled clinical trials can confirm a hypothesis about the effectiveness of a treatment independently of expectations. The blind method is a part of the Scientific method, used to prevent research outcomes from being influenced by either the Placebo effect or the Observer A sample is a subject chosen from a population for investigation Placebo is a substance or procedure a patient accepts as medicine or therapy but which has no specific therapeutic activity In health care clinical trials are conducted to allow safety and Efficacy data to be collected for new drugs or devices A hypothesis (from Greek) consists either of a suggested explanation for a phenomenon (an event that is observable or of a reasoned proposal suggesting a possible

Sites devoted to rhetoric [12] often give explanations along these lines:

Anecdotal evidence, for example, is by definition less statistically reliable than other sorts of evidence, and explanations do not carry the weight of authority. Rhetoric has had many definitions no simple definition can do it justice 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.

Law

Witness testimony is a common form of evidence in law, and law has mechanisms to test witness evidence for reliability or credibility. A witness is someone who has firsthand knowledge about a Crime or dramatic event through their Senses (e "Testify" redirects here For other uses see Testify (disambiguation and Testimony (disambiguation. The Law of evidence governs the use of Testimony (eg oral or written statements such as an Affidavit) and exhibits (e 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. Harassment refers to a wide spectrum of offensive behaviour The term commonly refers to behaviour intended to disturb or upset and when the term is used in a legal sense it refers In Law, a class action or a representative action is a form of Lawsuit where a large group of people collectively bring a claim to court 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.

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. The Daubert standard is a legal Precedent set in 1993 by the Supreme Court of the United States regarding the admissibility of Expert witnesses 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).

Miller and Miller (2005) list five standards of proof, by level of evidence [13]:

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:

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. " [14]

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. "[13]

References

  1. ^ Gibson, Rhonda and Zillman, Dolf. (1994). Exaggerated Versus Representative Exemplification in News Reports: Perception of Issues and Personal Consequences. Communication Research, 21(5), pp. 603–624.
  2. ^ Cambridge Advanced Learner's Dictionary
  3. ^ Dictionary.com
  4. ^ Merriam-Webster
  5. ^ YourDictionary.com
  6. ^ Jenicek M. "Clinical Case Reporting" in Evidence-Based Medicine. Oxford: Butterworth–Heinemann; 1999:117
  7. ^ Vandenbroucke JP (2001). In Defense of Case Reports and Case Series. Annals of Internal Medicine. Vol. 134:4, 300-334
  8. ^ 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
  9. ^ Thompson B. Fallacies.
  10. ^ Logic via infidels. org
  11. ^ Lee D (2005). Evaluating Medications and Supplement Products. via MedicineNet
  12. ^ Graham R. Anecdotes.
  13. ^ 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.
  14. ^ Altman DG, Bland M. Absence of evidence is not evidence of absence. British Medical Journal, 1995;311:485

Bibliography

See also

In Psychology and Cognitive science, confirmation bias is a tendency to search for or interpret new information in a way that confirms one's preconceptions and avoids A faulty generalization, also known as an inductive fallacy, is any of several errors of inductive inference: Logic The proportion Q of the sample Hasty generalization is a Logical fallacy of Faulty generalization by reaching an inductive Generalization based on insufficient Evidence Scientific method refers to bodies of Techniques for investigating phenomena Post hoc ergo propter hoc, Latin for "after this therefore because (on account of this" is a logical fallacy (of the Questionable cause variety

Dictionary

anecdotal evidence

-noun

  1. An informal form of hearsay obtained from random sources and having no legal basis.
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