7. Consider a probabilistic model that has a numerical parameter . A "probabilistic model" is just a set of assumptions about randomness. Let the random variable be an estimator of . Frequently, is a statistic based on a random sample. Recall that the bias of is defined as , where the subscript reminds us that is the true value of the parameter. The mean squared error of the estimator is . Follow the calculation in Section 12.2 of the textbook to show the bias-variance decomposition given by Note that the square in the bias term makes sense. Bias has the same units as , whereas the MSE and variance are in the square of those units