f(x)=12πσ2exp[−(x−μ)22σ2]f(x) = \frac{1}{\sqrt{2πσ^2}}\exp{[-\frac{(x-μ)^2}{2σ^2}]}f(x)=2πσ21exp[−2σ2(x−μ)2] 期待値(平均)の導出E(X)=∫−∞∞xf(x)dx=∫−∞∞(x−μ+μ)f(x)dx=∫−∞∞(x−μ)12πσ2exp[−(x−μ)22σ2]dx+∫−∞∞μf(x)dx=∫−∞∞(x−μσ)12πexp[−12(x−μσ)2]dx+μ∫−∞∞f(x)dx=∫−∞∞(x−μσ)12πexp[−12(x−μσ)2]σdxσ+μ\begin{equation*}\begin{split}E(X)&=\displaystyle \int_{ - \infty }^{ \infty } xf(x) dx\\ &=\displaystyle \int_{ - \in