X)=E(X2)=「Bx“e 令Bx rate pido dt r(a)0 (a)0(B +∞ 厂(a+2)F(a)a(a+1) BT(a) B r(a) 得方程组如下 nx B ∑(x1-x)2 (a+ nx. )( )( )()( dtet )( dte t )( dxex )( dxex )( )X(E)X(v t t tx x x 2 2 0 1 2 0 1 0 1 0 2 1 2 1 2 1 1 β αα αΓβ αΓαΓ αΓβ αΓ β β β αΓ β αΓ β α α β α βα α βα α + = + = = ⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = = = = ∫ ∫ ∫ ∫ ∞+ −+ ∞+ − + = ∞+ −+ ∞+ −+ 令 得方程组如下： ⎪ ⎪ ⎪ ⎩ ⎪ ⎪ ⎪ ⎨ ⎧ = − = = − = ⇒ ⎪ ⎪ ⎩ ⎪ ⎪ ⎨ ⎧ = + = ∑ ∑ ∑ = = = 2 1 2 2 2 1 2 2 1 2 2 11 σ β σ α β αα β α ~ x )xx( xn ˆ ~ x )xx( xn ˆ x n )( x n i i n i i n i i