Poisson Random Variable
$\displaystyle S_X=\{0,1,2,\ldots\}$
$\displaystyle p_k=\frac{\alpha^k}{k!}e^{-\alpha}$
$\displaystyle V[X]=\alpha$
$\displaystyle p_k=\frac{\alpha^k}{k!}e^{-\alpha}$
$\displaystyle k=0,1,\ldots$
$\displaystyle \alpha>0$
$\displaystyle E[X]=\alpha$$\displaystyle \alpha>0$
$\displaystyle V[X]=\alpha$
X는 한 시간 단위 당 사건의 횟수 - 사건 사이 시간이 평균 1/α인 지수 분포를 보일 때.
X is the number of events that occur in one time unit when the time between events is exponentially distributed with mean $\displaystyle 1/\alpha.$
X is the number of events that occur in one time unit when the time between events is exponentially distributed with mean $\displaystyle 1/\alpha.$