误差传递公式

1. 总的公式：

$$z = f(x,y)$$ $$\sigma_z^2 = \left({\partial f \over \partial x}\right)^2 \sigma_x^2 + \left({\partial f \over \partial y}\right)^2 \sigma_y^2$$

1. 示例：

$$\bar{x} = {1\over n}\sum_{i=1}^{n} x_i$$ $$\sigma_{\bar{x}} = {1\over n}\sqrt{\sum_{i=1}^{n} \sigma_{x_i}^2}$$