Normal 定义¶ 密度函数¶ \[ f(x)=\frac{1}{\sqrt{2 \pi} \sigma} \exp \left(-\frac{(x-\mu)^{2}}{2 \sigma^{2}}\right) \] 有趣的性质¶ \[ \text { 若 } X \sim N\left(\mu, \sigma^{2}\right), Y=\frac{X-\mu}{\sigma} \sim N(0,1) \]