Anecdotal evidence

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Anecdotal evidence (anecdotal statement, anecdotal evidence, case report) is an informal report of evidence in the form of a single report or hearsay . The term is often used as a contrast to empirical evidence (e.g. clinical studies , laboratory studies , field studies ) and to infer by analogy . Anecdotal evidence has poor argumentative power.

Anecdotal evidence can be compiled using narratological methods.

definition

The term anecdotal evidence involves an accurate description of a specific example or case, often reflecting the descriptor's opinion or experience. These case descriptions are neither statistically nor scientifically verifiable in any other way, are often unreliable and are therefore considered epistemically problematic. In some respects, the anecdotal evidence serves as a contrast to the statistical evidence due to its weakness.

application areas

Misuse of anecdotal evidence is a logical fallacy and is sometimes informally referred to as the “someone who” fallacy (“I know someone who ...”, “I know of a case where ...”), comparable to hasty generalization. Anecdotal evidence is not necessarily typical. Statistical evidence can more accurately determine how typical something is.

With all forms of anecdotal evidence, there may be doubts as to whether its reliability can be tested by objective, independent research. This is a consequence of the informal way in which this information is collected, documented and / or presented. The term is often used to refer to evidence for which there is no documentation. This means that verification depends on the credibility of the party presenting the evidence.

The argument based on anecdotal evidence can be traced back to the philosophical concept of induction , in which observation is based on regularities. Since the discussion of the induction problem by the philosopher David Hume , this type of argument has been called into question in philosophy.

science

General

The endeavor of anecdotal evidence is to be distinguished from that of statistical evidence, which consists in deriving general trends and patterns. For statistical evidence, the number of cases examined determines the reliability and evidence of the information. An important element of the statistical investigation are, for example, the questions and their formulation. The precise design of the questions should guarantee that the respondents' answers are not predetermined or subjectively influenced. In contrast, the anecdotal evidence does not or hardly deals with verifiable trends and patterns, but rather with a detailed presentation of special cases or examples. Researchers who actually use the anecdotal evidence often tend to authorize results when a large number of small examples or cases suggest a trend. According to scientific understanding, however, an individual case cannot provide any information about trends, population groups or frequencies.

In the social sciences , John Forrester cited a model of action knowledge that all knowledge is based only on case-by-case reasoning.

medicine

In medicine, anecdotal evidence is of great importance. Miraculous healing cases are intended to refute clinical or scientific studies and point to a contradicting conclusion. Anecdotal statements about similar clinical pictures and their outcome are often more interesting and clear to patients than mere statistics. The scientists Ubel, Jepson and Baron were able to confirm this with a series of experiments. Her research question was: "What is decisive for the treatment decision of patients?" The experimental set-up provided that the participants were provided with fictitious statistical information on the percentage of cardiac patients whose state of health has improved through vasodilation or bypass surgery. On the other hand, they received letters of recommendation from hypothetical patients who either benefited or did not benefit from one of the procedures mentioned.

psychotherapy

In psychotherapy research , single case studies used traditional. A distinction is made between efficacy - studies (efficacy of psychotherapy under ideal conditions) and Effectiveness Studies (effectiveness of psychotherapy under real conditions).

everyday life

Anecdotal statements can be very convincing in everyday life and are referred to as the “someone who” fallacy. Examples of anecdotal statements are often introduced with "I know someone who ..." or "I know about a case in which ...". A psychological study found that students relied more on the statements of individual students in choosing their courses than on statistics that reflected how a representative majority rated the course. The reason given for this is that a story is much more tangible and therefore easier to remember.

Anecdotal evidence is not always incorrect or untrue, it is often simply based on a false conclusion. An example of this is: "My grandfather smoked like a chimney, but died perfectly healthy in a car accident at the age of 99." The statement cannot disprove the fact that smoking markedly increases the likelihood of various diseases, nor can it the opposite occupy. In this case, the evidence may actually be there, but it does not guarantee the conclusion. The generalization of this one case to other similar cases is also impossible, since the given circumstances and the behavior of the protagonists can differ. Thus an anecdotal statement, however high its truth content may be, cannot be used as scientifically valuable evidence.

Of course, this applies to the statistical estimation of probabilities . Is an existence statement actually intended, e.g. For example, “it is at least possible that”, the anecdotal evidence is useful if it is only truthful.

advertising

The principle of anecdotal evidence is increasingly used in advertising in order to generate trust in the product in the audience based on the experiences and stories of others. The presentation of the product by so-called experts is particularly credible. A dentist's advertising for a particular brand of toothpaste is considered particularly credible.

Significance for communication and argumentation theory

The distinction between statistical and anecdotal evidence plays an important role in communication and argumentation theory . Hoeken and Hustinx deal with the quality of arguments in one of their studies. In corresponding experiments, they found that the persuasiveness of both types of evidence crucially depends on the type of argument used. When an argument is based on a generalization, statistical evidence is usually more convincing. But if the argument is based on an analogy , the statistical and anecdotal evidence for the participants in the experiment is equally convincing.

Furthermore, it is partly argued in science that the respective cultural background is relevant to which types of evidence are considered more convincing.

Individual evidence

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  7. ^ PA Ubel, C. Jepson, J. Baron: The inclusion of patient testimonials in decision aids: Effects on treatment choices . Medical Decision Making, 21 (2001), pp. 60-68.
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literature

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