My pdf for $X$ is $$f_X ( x ; \theta ) = (1/\theta) x \exp (-x/\theta).$$
I am unsure as to how to show that the mean value of $X$ is $\theta$?
My pdf for $X$ is $$f_X ( x ; \theta ) = (1/\theta) x \exp (-x/\theta).$$
I am unsure as to how to show that the mean value of $X$ is $\theta$?