10 Generalized Linear Regression
In the problems of this section
$$x^T\beta = \beta_0 + \sum_{i=1}^p \beta_i x_i$$
Problem 10.5.
Y is an exponentially distributed random variable with parameter $\lambda > 0$, we write Y ~
Exp($\lambda$), if its probability density function is
$$f(y;\lambda) = \begin{cases}
\lambda e^{-\lambda y} & y \ge 0, \\
0 & y < 0.
\end{cases}$$
$\lambda$ is sometimes called the rate parameter. We want to construct a generalized linear model
(exponential regression). We know that E[Y] = 1/$\lambda$, this need not be derived here.
a) Find the canonical link function relating $x^T\beta$ to the mean. What does this require from
$x^T\beta$?
b) Write down the probability density function
$$f(y; x^T\beta).$$
c) What is E[Y|x] in exponential regression?