PLAYGROUND

ECUACIONES DISTRIBUCIÓN CHI CUADRADO NO CENTRAL

Definición de distribución

XNonCentralChiSquare(λ,n)X\sim\mathrm{NonCentralChiSquare}\left(\lambda,n\right)

Dominio de distribución

x[0,+)x\in [0,+\infty)

Dominio y restricciones de parámetros

λR+,nR+\lambda\in\mathbb{R}^{+},n\in\mathbb{R}^{+}

Función de distribución acumulada

FX(x)=1Qn2(λ,x)F_{X}\left(x\right)=1-Q_{\frac{n}{2}}\left(\sqrt{\lambda},\sqrt{x}\right)

Función de densidad de probabilidad

fX(x)=12e(x+λ)/2(xλ)n/41/2In/21(λx)f_{X}\left(x\right)=\frac{1}{2}e^{-(x+\lambda)/2} \left(\frac{x}{\lambda}\right)^{n/4-1/2}I_{n/2-1}(\sqrt{\lambda x})

Función de punto percentil

SampleX=i=1n(λn+Φ1(ui))2\text{Sample}_{X}=\sum_{i=1}^{n}\left(\sqrt{\frac{\lambda}{n}}+\Phi^{-1}\left(u_{i}\right)\right)^{2}

Momentos paramétricos no centrados

μk=E[Xk]=0xkfX(x)dx=2k1(k1)!(n+kλ)+j=1k1(k1)!2j1(kj)!(n+jλ)μkj\mu'_{k}=E[X^k]=\int_{0}^{\infty}x^{k}f_{X}\left(x\right)dx=2^{k-1}(k-1)!(n+k\lambda)+\sum_{j=1}^{k-1}\frac{(k-1)!2^{j-1}}{(k-j)!}(n+j\lambda )\mu'_{k-j}

Media paramétrica

Mean(X)=μ1=n+λ\mathrm{Mean}(X)=\mu'_{1}=n+\lambda

Varianza paramétrica

Variance(X)=μ2μ12=2(n+2λ)\mathrm{Variance}(X)=\mu'_{2}-\mu'^{2}_{1}=2(n+2\lambda)

Coeficiente de asimetría paramétrico

Skewness(X)=μ33μ2μ1+2μ13(μ2μ12)1.5=23/2(n+3λ)(n+2λ)3/2\mathrm{Skewness}(X)=\frac{\mu'_{3}-3\mu'_{2}\mu'_{1}+2\mu'^{3}_{1}}{(\mu'_{2}-\mu'^{2}_{1})^{1.5}}=\frac{2^{3/2}(n+3\lambda)}{(n+2\lambda)^{3/2}}

Curtosis paramétrica

Kurtosis(X)=μ44μ1μ3+6μ12μ23μ14(μ2μ12)2=12(n+4λ)(n+2λ)2\mathrm{Kurtosis}(X)=\frac{\mu'_{4}-4\mu'_{1}\mu'_{3}+6\mu'^{2}_{1}\mu'_{2}-3\mu'^{4}_{1}}{(\mu'_{2}-\mu'^{2}_{1})^{2}}=\frac{12(n+4\lambda)}{(n+2\lambda)^2}

Mediana paramétrica

Median(X)=FX1(12)\mathrm{Median}(X)=F^{-1}_{X}\left(\frac{1}{2}\right)

Moda paramétrica

Mode(X)=argmaxxfX(x)\mathrm{Mode}(X)=\arg\max_{x}f_{X}\left(x\right)

Información y definiciones adicionales

Computing an analytic expression for the inverse of the cumulative distribution function is notfeasible. Nonetheless, it is possible to generate a random sample from the distribution.\text{Computing an analytic expression for the inverse of the cumulative distribution function is not} \\ \text{feasible. Nonetheless, it is possible to generate a random sample from the distribution.}
ui:Uniform[0,1] random varibleu_{i}:\text{Uniform[0,1] random varible}
Φ1(x):PPF normal standard distribution\Phi^{-1}\left(x\right):\text{PPF normal standard distribution}
Iα(x):Modified Bessel function of the first kind of order αNI_{\alpha}\left(x\right):\text{Modified Bessel function of the first kind of order }\alpha\in\mathbb{N}