Noncentral BetaNotation |
Beta(α, β, λ) |
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Parameters |
α > 0 shape (real) β > 0 shape (real) λ ≥ 0 noncentrality (real) |
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Support |
![{\displaystyle x\in [0;1]\!}](https://wikimedia.org/api/rest_v1/media/math/render/svg/394f69db847ba283727b0bc73bccc019572a72ae) |
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PDF |
(type I) ![{\displaystyle \sum _{j=0}^{\infty }e^{-\lambda /2}{\frac {\left({\frac {\lambda }{2}}\right)^{j}}{j!}}{\frac {x^{\alpha +j-1}\left(1-x\right)^{\beta -1}}{\mathrm {B} \left(\alpha +j,\beta \right)}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e2f416e3014c4f6d7feb383e1a675cf5a350a8f5) |
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CDF |
(type I) ![{\displaystyle \sum _{j=0}^{\infty }e^{-\lambda /2}{\frac {\left({\frac {\lambda }{2}}\right)^{j}}{j!}}I_{x}\left(\alpha +j,\beta \right)}](https://wikimedia.org/api/rest_v1/media/math/render/svg/1c5f69f89b3478df9b2976844884e77793af99eb) |
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Mean |
(type I) (see Confluent hypergeometric function) |
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Variance |
(type I) where is the mean. (see Confluent hypergeometric function) |
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In probability theory and statistics, the noncentral beta distribution is a continuous probability distribution that is a noncentral generalization of the (central) beta distribution.
The noncentral beta distribution (Type I) is the distribution of the ratio
![{\displaystyle X={\frac {\chi _{m}^{2}(\lambda )}{\chi _{m}^{2}(\lambda )+\chi _{n}^{2}}},}](https://wikimedia.org/api/rest_v1/media/math/render/svg/3e92c23ac937619950544b8dc06a574a4b1e495a)
where
is a
noncentral chi-squared random variable with degrees of freedom m and noncentrality parameter
, and
is a central chi-squared random variable with degrees of freedom n, independent of
.[1]
In this case,
A Type II noncentral beta distribution is the distribution
of the ratio
![{\displaystyle Y={\frac {\chi _{n}^{2}}{\chi _{n}^{2}+\chi _{m}^{2}(\lambda )}},}](https://wikimedia.org/api/rest_v1/media/math/render/svg/981969faaa19262fa1725a4d7ff65893b9cacb5c)
where the noncentral chi-squared variable is in the denominator only.[1] If
follows
the type II distribution, then
follows a type I distribution.
- ^ a b Chattamvelli, R. (1995). "A Note on the Noncentral Beta Distribution Function". The American Statistician. 49 (2): 231–234. doi:10.1080/00031305.1995.10476151.