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Difference between revisions of "Likelihood equation"

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An equation obtained by the [[Maximum-likelihood method|maximum-likelihood method]] when finding statistical estimators of unknown parameters. Let <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588001.png" /> be a random vector the probability density <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588002.png" /> of which contains an unknown parameter <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588003.png" />. Then the equation
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An equation obtained by the [[maximum-likelihood method]] when finding statistical estimators of unknown parameters. Let $X$ be a random vector for which the probability density $p(x|\theta)$ contains an unknown parameter $\theta \in \Theta$. Then the equation
 
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$$
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588004.png" /></td> </tr></table>
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\frac{\partial}{\partial\theta} \log p(X|\theta) = 0
 
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$$
is called the likelihood equation and its solution <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588005.png" /> is called the maximum-likelihood estimator for <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058800/l0588006.png" />. In some cases the likelihood equation can be solved in an elementary way. However, in general, the likelihood equation is an algebraic or transcendental equation, solved by the method of successive approximation (cf. [[Sequential approximation, method of|Sequential approximation, method of]]).
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is called the likelihood equation and its solution $\hat\theta$ is called the maximum-likelihood estimator for $\theta$. In some cases the likelihood equation can be solved in an elementary way. However, in general, the likelihood equation is an algebraic or transcendental equation, solved by the method of successive approximation (cf. [[Sequential approximation, method of|Sequential approximation, method of]]).
  
 
====References====
 
====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  B.L. van der Waerden,  "Mathematische Statistik" , Springer  (1957)</TD></TR></table>
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<TR><TD valign="top">[1]</TD> <TD valign="top">  B.L. van der Waerden,  "Mathematische Statistik" , Springer  (1957) {{ZBL|0077.12901}}</TD></TR>
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====References====
 
====References====
<table><TR><TD valign="top">[a1]</TD> <TD valign="top">  D.R. Cox,  D.V. Hinkley,  "Theoretical statistics" , Chapman &amp; Hall  (1974)  pp. 21</TD></TR></table>
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<TR><TD valign="top">[a1]</TD> <TD valign="top">  D.R. Cox,  D.V. Hinkley,  "Theoretical statistics" , Chapman and Hall  (1974)  pp. 21 {{ZBL|0334.62003}}</TD></TR>
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Latest revision as of 18:13, 19 November 2016

An equation obtained by the maximum-likelihood method when finding statistical estimators of unknown parameters. Let $X$ be a random vector for which the probability density $p(x|\theta)$ contains an unknown parameter $\theta \in \Theta$. Then the equation $$ \frac{\partial}{\partial\theta} \log p(X|\theta) = 0 $$ is called the likelihood equation and its solution $\hat\theta$ is called the maximum-likelihood estimator for $\theta$. In some cases the likelihood equation can be solved in an elementary way. However, in general, the likelihood equation is an algebraic or transcendental equation, solved by the method of successive approximation (cf. Sequential approximation, method of).

References

[1] B.L. van der Waerden, "Mathematische Statistik" , Springer (1957) Zbl 0077.12901


Comments

References

[a1] D.R. Cox, D.V. Hinkley, "Theoretical statistics" , Chapman and Hall (1974) pp. 21 Zbl 0334.62003
How to Cite This Entry:
Likelihood equation. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Likelihood_equation&oldid=19118
This article was adapted from an original article by M.S. Nikulin (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article