对于均值为$$$2$$$的泊松分布，求$$$P{\left(X = 1 \right)}$$$

用 $$$\lambda = 2$$$ 和 $$$x = 1$$$ 计算泊松分布的各项数值。

平均值：$$$\mu = \lambda = 2$$$A。

方差：$$$\sigma^{2} = \lambda = 2$$$A。

标准差: $$$\sigma = \sqrt{\lambda} = \sqrt{2}\approx 1.414213562373095$$$A.

$$$P{\left(X = 1 \right)}\approx 0.270670566473225$$$A

$$$P{\left(X \lt 1 \right)}\approx 0.135335283236613$$$A

$$$P{\left(X \leq 1 \right)}\approx 0.406005849709838$$$A

$$$P{\left(X \gt 1 \right)}\approx 0.593994150290162$$$A

$$$P{\left(X \geq 1 \right)}\approx 0.864664716763387$$$A