全题为：“设总体X的概率密度为：f(x,θ)=e的[-(x-θ)]次方，x≥θ；0，x<θ。...答：EX=∫(上+∞下θ)xf(x,θ)dx=∫(上+∞下θ)xe^[-(x-θ)]dx =-(xe^[-(x-θ)]|(上+∞下θ)-∫(上+∞下θ)e^[-(x-θ)]dx) =-θ-1=µ θ=-µ-1 θ^=-￣X-1(X左边横线在X上方) 其中￣X=1/n∑(从1到n)Xi
