Theorem

Fisher's Inequality

Combinatorics and Graph Theory

Fisher's Inequality states that in any balanced incomplete block design, a combinatorial arrangement of points into blocks in which every pair of points appears together in the same fixed number of blocks, the number of blocks can never be smaller than the number of points. Named for Ronald Fisher, it is a foundational result of combinatorial design theory.

Facts
Statement
In a balanced incomplete block design with v points and b blocks, b is at least v. 2
Proof Year
1940 2
Classification
Statement Form
Existence Theorem 1
Fisher's Inequality
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Source Fisher's inequality (Wikipedia)

Principal Result Of

Source Fisher's inequality (Wikipedia)

Proved By

Source Fisher's inequality (Wikipedia)
Sources
1. Wikipedia: Fisher's inequality
WikipediaLead section, statement-form reference
Quote, Lead section, statement-form reference
Fisher's inequality is a necessary condition for the existence of a balanced incomplete block design, that is, a system of subsets that satisfy certain prescribed conditions in combinatorial mathematics.
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2. Fisher's inequality (Wikipedia)
  • Introduction
    Fisher's inequality states simply that b ≥ v.
  • References
    R. A. Fisher, 'An examination of the different possible solutions of a problem in incomplete blocks', Annals of Eugenics, volume 10, 1940
  • Principal Result Of: Ronald Fisher, Lead sentence of the article on the result
    Outlined by Ronald Fisher, a population geneticist and statistician, who was concerned with the design of experiments such as studying the differences among several different varieties of plants, under each of a number of different growing conditions, called blocks.
  • Proved By: Ronald Fisher, Lead paragraph
    Fisher's inequality is a necessary condition for the existence of a balanced incomplete block design, that is, a system of subsets
  • In Group: Enumerative, Additive and Algebraic Combinatorics, Lead section
    of subsets that satisfy certain prescribed conditions in combinatorial mathematics. Outlined by Ronald Fisher, a population geneticist
  • In Branch: Combinatorics, Lead section
    of subsets that satisfy certain prescribed conditions in combinatorial mathematics. Outlined by Ronald Fisher, a population
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