Mean squared error: Difference between revisions

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&= \operatorname{E}_{\theta}\left[\left(\hat{\theta}-\operatorname{E}_{\theta}[\hat\theta]\right)^2\right]+ 2 \left(\operatorname{E}_{\theta}[\hat\theta]-\theta\right) \operatorname{E}_{\theta}\left[\hat{\theta}-\operatorname{E}_{\theta}[\hat\theta] \right] + \left(\operatorname{E}_{\theta}[\hat\theta]-\theta\right)^2 && \operatorname{E}_{\theta}[\hat\theta]-\theta = \text{const.} \\
&= \operatorname{E}_{\theta}\left[\left(\hat{\theta}-\operatorname{E}_{\theta}[\hat\theta]\right)^2\right]+ 2 \left(\operatorname{E}_{\theta}[\hat\theta]-\theta\right) \left ( \operatorname{E}_{\theta}[\hat{\theta}]-\operatorname{E}_{\theta}[\hat\theta] \right )+ \left(\operatorname{E}_{\theta}[\hat\theta]-\theta\right)^2 && \operatorname{E}_{\theta}[\hat\theta] = \text{const.} \\
&= \operatorname{E}_{\theta}\left[\left(\hat{\theta}-\operatorname{E}_{\theta}[\hat\theta]\right)^2\right]+\left(\operatorname{E}_{\theta}[\hat\theta]-\theta\right)^2\\
&= \operatorname{Var}_{\theta}(\hat\theta)+ \operatorname{Bias}_{\theta}(\hat\theta,\theta)^2
\end{align}</math>