PLAYGROUND

ECUACIONES DISTRIBUCIÓN BINOMIAL NEGATIVA

Definición de distribución

XNegativeBinomial(r,p)X\sim\mathrm{NegativeBinomial}\left(r,p\right)

Dominio de distribución

xN{0,1,2,}x\in\mathbb{N}\equiv \left\{0,1,2,\dots\right\}

Dominio y restricciones de parámetros

rN1,p(0,1)Rr\in\mathbb{N}_{\geqslant 1},p\in\left(0,1\right)\subseteq\mathbb{R}

Función de distribución acumulada

FX(x)=I(p,r,x+1)F_{X}\left(x\right)=I(p,r,x+1)

Función de masa de Probabilidad

fX(x)=(r+x1x)pr(1p)xf_{X}\left(x\right)=\binom{r+x-1}{x}p^r(1-p)^x

Función de punto percentil

FX1(u)=argminxFX(x)uF^{-1}_{X}\left(u\right)=\arg\min_{x}\left| F_{X}\left(x\right)-u \right|

Momentos centrados paramétricos

E[Xk]=μk=x=0xkfX(x)E[X^k]=\mu'_{k}=\sum_{x=0}^{\infty}x^{k}f_{X}\left(x\right)

Media paramétrica

Mean(X)=μ1=r(1p)p\mathrm{Mean}(X)=\mu'_{1}=\frac{r(1-p)}{p}

Varianza paramétrica

Variance(X)=(μ2μ12)=r(1p)p2\mathrm{Variance}(X)=(\mu'_{2}-\mu'^{2}_{1})=\frac{r(1-p)}{p^2}

Coeficiente de asimetría paramétrico

Skewness(X)=μ33μ2μ1+2μ13(μ2μ12)1.5=2pr(1p)\mathrm{Skewness}(X)=\frac{\mu'_{3}-3\mu'_{2}\mu'_{1}+2\mu'^{3}_{1}}{(\mu'_{2}-\mu'^{2}_{1})^{1.5}}=\frac{2-p}{\sqrt{r\,(1-p)}}

Curtosis paramétrica

Kurtosis(X)=μ44μ1μ3+6μ12μ23μ14(μ2μ12)2=3+6r+p2r(1p)\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}}=3+\frac{6}{r} + \frac{p^2}{r\,(1-p)}

Mediana paramétrica

Median(X)=FX1(0.5)\mathrm{Median}(X)=F^{-1}_{X}\left(0.5\right)

Moda paramétrica

Mode(X)=(r1)(1p)/p\mathrm{Mode}(X)=\lfloor(r-1)\,(1-p)/p\rfloor

Información y definiciones adicionales

Computing an analytic expression for the inverse of the cumulative distribution functionis not feasible. However, it is possible to calculate the Percentile Point Function byapproximating it to the nearest integer.\text{Computing an analytic expression for the inverse of the cumulative distribution function} \\ \text{is not feasible. However, it is possible to calculate the Percentile Point Function by} \\ \text{approximating it to the nearest integer.}
u:Uniform[0,1] random varibleu:\text{Uniform[0,1] random varible}
I(x,a,b):Regularized incomplete beta functionI\left(x,a,b\right):\text{Regularized incomplete beta function}
x:Floor function\lfloor{x}\rfloor: \text{Floor function}