View source for Philosophy:Texas sharpshooter fallacy

{{Short description|Statistical fallacy}}
The '''Texas sharpshooter fallacy''' is an [[Informal fallacy|informal fallacy]] which is committed when differences in data are ignored, but similarities are overemphasized. From this reasoning, a false conclusion is inferred.<ref>{{citation |entry=Texas sharpshooter fallacy |last=Bennett |first=Bo |title=Logically Fallacious |access-date=21 October 2014 |entry-url= https://www.logicallyfallacious.com/logicalfallacies/Texas-Sharpshooter-Fallacy | quote = description: ignoring the difference while focusing on the similarities, thus coming to an inaccurate conclusion}}</ref> This fallacy is the philosophical or rhetorical application of the multiple comparisons problem (in statistics) and [[Apophenia|apophenia]] (in cognitive psychology). It is related to the [[Clustering illusion|clustering illusion]], which is the tendency in human [[Cognition|cognition]] to interpret patterns where none actually exist.

The name comes from a metaphor about a person from {{wipe|Texas}} who fires a gun at the side of a barn, then paints a [[Engineering:Shooting target|shooting target]] centered on the tightest [[Engineering:Shot grouping|cluster]] of shots and claims to be a sharpshooter.<ref>{{cite web|url=http://www.barrypopik.com/index.php/texas/entry/texas_sharpshooter_fallacy/|title=Texas Sharpshooter Fallacy|author=Barry Popik|publisher=barrypopik.com|date=2013-03-09|access-date=2015-11-10}}</ref><ref>{{cite magazine|url=http://www.crab.rutgers.edu/~mbravo/cluster.pdf|title=The cancer-cluster myth|author=Atul Gawande|magazine=The New Yorker|date=1999-08-02|access-date=2009-10-10}}</ref><ref>{{cite book | last1 = Carroll | first1 = Robert Todd |  title = The Skeptic's Dictionary: a collection of strange beliefs, amusing deceptions, and dangerous delusions | publisher = John Wiley & Sons | year = 2003 | page = 375 | url = https://books.google.com/books?id=6FPqDFx40vYC&q=texas+sharpshooter&pg=PA375 | access-date = 2012-03-25 | isbn = 0-471-27242-6 | quote = The term refers to the story of the Texan who shoots holes in the side of a barn and then draws a bull's-eye around the bullet holes}}</ref>

== Structure ==
[[File:Texas Sharpshooter Fallacy illustration.png|thumb|A set of 100 randomly generated points displayed on a scatter graph. Examining the points, it is easy to identify apparent patterns. In particular, rather than spreading out evenly, it is not uncommon for random data points to form clusters, giving the (false) impression of "hot spots" created by some underlying cause.]]
The Texas sharpshooter fallacy often arises when a person has a large amount of data at their disposal but only focuses on a small subset of that data. Some factor other than the one attributed may give all the elements in that subset some kind of common property (or pair of common properties, when arguing for correlation). If the person attempts to account for the likelihood of finding ''some'' subset in the large data with ''some'' common property by a factor other than its actual cause, then that person is likely committing a Texas sharpshooter fallacy.

The fallacy is characterized by a lack of a specific hypothesis prior to the gathering of data, or the formulation of a hypothesis only after data have already been gathered and examined.<ref>{{cite journal | title = Painting the target around the matching profile: the Texas sharpshooter fallacy in forensic DNA interpretation | journal = Law, Probability, & Risk | date = July 18, 2009 | first = William C. | last = Thompson | volume = 8 | issue = 3 | pages = 257–258| url = http://lpr.oxfordjournals.org/content/8/3/257.full.pdf+html | access-date = 2012-03-25 | quote = Texas sharpshooter fallacy...this article demonstrates how post hoc target shifting occurs and how it can distort the frequency and likelihood ratio statistics used to characterize DNA matches, making matches appear more probative than they actually are. | doi=10.1093/lpr/mgp013| doi-access = free }}</ref> Thus, it typically does not apply if one had an ''ex ante'', or prior, expectation of the particular relationship in question before examining the data. For example, one might, prior to examining the information, have in mind a specific physical mechanism implying the particular relationship. One could then use the information to give support or cast doubt on the presence of that mechanism. Alternatively, if a second set of additional information can be generated using the same process as the original information, one can use the first (original) set of information to construct a hypothesis, and then test the hypothesis on the second (new) set of information. (See hypothesis testing.) However, after constructing a hypothesis on a set of data, one would be committing the Texas sharpshooter fallacy if they then tested that hypothesis on the same data (see hypotheses suggested by the data).

== Examples ==
A Swedish study in 1992 tried to determine whether [[Biology:Electromagnetic radiation and health|power lines caused some kind of poor health effects]].<ref>{{Cite journal|last1=Feychting|first1=M.|last2=Ahlbom|first2=A.|date=1993-10-01|title=Magnetic fields and cancer in children residing near Swedish high-voltage power lines|url=https://pubmed.ncbi.nlm.nih.gov/8213751/|journal=American Journal of Epidemiology|volume=138|issue=7|pages=467–481|doi=10.1093/oxfordjournals.aje.a116881|issn=0002-9262|pmid=8213751}}</ref> The researchers surveyed people living within 300 meters of [[Engineering:Overhead power line|high-voltage power lines]] over 25 years and looked for statistically significant increases in rates of over 800 ailments. The study found that the incidence of childhood leukemia was four times higher among those who lived closest to the power lines, and it spurred calls to action by the Swedish government.<ref>{{Cite web|url=https://www.newscientist.com/article/mg13618450-300-swedish-studies-pinpoint-power-line-cancer-link/|title=Swedish studies pinpoint power line cancer link|first=Andy|last=Coghlan|website=New Scientist}}</ref> The problem with the conclusion, however, was that the number of potential ailments, i.e., over 800, was so large that it created a high probability that at least one ailment would exhibit the appearance of a statistically significant difference by chance alone, a situation known as the [[Multiple comparisons problem|multiple comparisons problem]]. Subsequent studies failed to show any association between power lines and childhood leukemia.<ref>{{cite web|url=https://www.pbs.org/wgbh/pages/frontline/programs/transcripts/1319.html |title=Frontline: previous reports: transcripts: currents of fear |website=PBS |date=1995-06-13 |access-date=2012-07-03|archive-url=https://web.archive.org/web/20160203040412/http://www.pbs.org/wgbh/pages/frontline/programs/transcripts/1319.html|archive-date=2016-02-03}}</ref>

The fallacy is often found in modern-day interpretations of the quatrains of [[Biography:Nostradamus|Nostradamus]]. Nostradamus's quatrains are often liberally translated from their original (archaic) French versions, in which their historical context is often lost, and then applied to support the erroneous conclusion that Nostradamus predicted a given modern-day event after the event actually occurred.<ref>{{cite web|url=http://www.snopes.com/rumors/nostradamus.asp |title=Nostradamus Predicted 9/11? |website=snopes.com|date=12 September 2001 |access-date=2012-07-03}}</ref>

== See also ==
{{div col}}
* {{annotated link|Astronomy:Anthropic principle}} 
* {{annotated link|Availability heuristic}}
* {{annotated link|Confirmation bias}} 
* {{annotated link|Data dredging}}, also known as p-hacking
* {{annotated link|HARKing}} 
* {{annotated link|Look-elsewhere effect}} 
* {{annotated link|Overfitting}} 
* {{annotated link|Postdiction}} 
* {{annotated link|Ramsey theory}} 
* {{annotated link|Scan statistic}} 
{{div col end}}

=== Related fallacies ===
* {{annotated link|Philosophy:Correlative-based fallacies}} 
* ''{{annotated link|Philosophy:Post hoc ergo propter hoc}}''

== References ==
{{Reflist}}

== External links ==
* [http://www.fallacyfiles.org/texsharp.html Fallacy files entry]

{{Fallacies}}

[[Category:Causal fallacies]]
[[Category:Cognitive biases]]

{{Sourceattribution|Texas sharpshooter fallacy}}