[問題] E(SSE) 過程推導
iid
Y=b0+b1X1+....+b_(k-1)X_(k-1)+ε ,ε ~ N(0,σ^2)
indep
Yi ~ N(μi ,σ^2)
Y:由k-1個解釋變數組成的複迴歸
E(SSE)=E(Σ(Y_i-Y_i(hat))^2)
=ΣE[(Y_i-μ_i)-(Y_i(hat)-E(Y_i(hat)))+(μ_i-E(Y_i(hat)))]^2
?
=ΣE(Y_i-μ_i)^2 -ΣE(Y_i(hat)-E(Y_i(hat)))^2
+Σ(μ_i-E(Y_i(hat))^2
請問這個等號怎麼來的?
將第二個等號中間展開後,我只能推出下列式子
ΣE(Y_i-μ_i)^2 +ΣE(Y_i(hat)-E(Y_i(hat)))^2 +Σ(μ_i-E(Y_i(hat))^2
-2ΣE(Y_i-μ_i)(Y_i(hat)-E(Y_i(hat)))
+2ΣE(Y_i-μ_i)(μ_i-E(Y_i(hat))
~~~~~~~~~~~~~~~~~~~~~~~~~
||
0
-2ΣE(Y_i(hat)-E(Y_i(hat)))(μ_i-E(Y_i(hat))
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
||
0
從結果來看 應該是
E(Y_i-μ_i)(Y_i(hat)-E(Y_i(hat))) = E(Y_i(hat)-E(Y_i(hat)))^2
所以得到一開始第三個等號的式子,請問這是怎麼來的呀?
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