10 Generalized Linear Regression
In the problems of this section
$$x^T\beta = \beta_0 + \sum_{i=1}^p \beta_i x_i$$
Problem 10.4.
Consider the normal multiple least squares model,
$$Y^* = x^T\beta + \epsilon,$$
(134)
where $x^T = (1, x_1, x_2, ..., x_p)$, $\beta^T = (\beta_0, \beta_1, ..., \beta_p)$ and $\epsilon \sim N(0, 1)$, and is independent of $x$.
a) Explain why we have
$$P(-\epsilon \leq x) = P(\epsilon \leq x).$$
(135)
Aid: Let $\Phi(x)$ be the cumulative distribution function of $N(0,1)$ and $\phi(x)$ be the corresponding pdf. Since $\phi(x) = \phi(-x)$, we have
$$\Phi(-x) = 1 - \Phi(x).$$
b) Construct
Verify that
$$Y = \begin{cases}
1 & \text{if } Y^* > 0, \\
0 & \text{otherwise}.
\end{cases}$$
$$P(Y = 1 | x) = \Phi(x^T\beta),$$
You may use (135) even if you have failed to show it.
c) The r.v. Y in this assignment is a special case of generalized linear regression (GLM). The
way to construct a GLM goes via a link function. Present and justify the link function in
this assignment.