$MSE(\hat{\theta}) = Var(\hat{\theta}) + Bias(\hat{\theta})$

$MSE(\hat{\theta}) = Var(\hat{\theta}) + (Bias(\hat{\theta}))^2$

$MSE(\hat{\theta}) = \sqrt{Var(\hat{\theta})} + Bias(\hat{\theta})$

$MSE(\hat{\theta}) = Var(\hat{\theta}) - (Bias(\hat{\theta}))^2$