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Parsimony is the taking of extreme care at arriving at a course of action; or unusual or excessive frugality, extreme economy or stinginess. The word derives from Middle English parcimony, from Latin parsimonia, from parsus, past participle of parcere to spare.

[edit] Science

In science, parsimony is preference for the least complicated explanation for an observation. This is generally regarded as good when judging hypotheses. Occam's Razor also states the "principle of parsimony".

In systematics, maximum parsimony is a cladistic optimality criterion based on the principle of parsimony. Under maximum parsimony, the preferred phylogenetic tree is the tree that requires the least number of evolutionary changes.

In biogeography, parsimony is used to infer ancient migrations of species or populations by observing the geographic distribution and relationships of existing organisms. Given the phylogenetic tree, ancestral migrations are inferred to be those that require the minimum amount of total movement.

Parsimony is also a factor in statistics: in general, mathematic models with the smallest number of parameters are preferred as each parameter introduced into the model adds some uncertainty to it. Additionally, adding too many parameters leads to "connect-the-dots" curve-fitting which has little predictive power. In general terms, it may be said that applied statisticians (such as process control engineers) value parsimony quite highly, whereas mathematicians prefer to have a more predictive model even if a large number of parameters are required.

[edit] See also

• Occam's Razor
• Maximum parsimony
• Cladistics
• Karl Popper
• Willi Hennig

[edit] External link

• Essay about parsimony in philosophy and science
• A short blog entry about statistical parsimony

This page uses content from the English-language version of Wikipedia. The original article was at Parsimony. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License.