# Moment generating function for geometric

• Aug 14th 2011, 05:29 PM
whiteboard
Moment generating function for geometric
geometric distribution given by

$Pr(X=x) = (1/a)(1-(1/a)^{x-1})$ where a > 1.

Am I right in saying the distribution above is the same as

$Pr(X=x) = p(1-p)^{x-1}$ which is just the normal geometric pdf or does the change from p to 1/a change something else
• Aug 15th 2011, 01:17 AM
Moo
Re: Moment generating function for geometric
Hello,

It doesn't change anything, but I just don't understand where the MGF is in there ?
• Aug 15th 2011, 11:20 PM
CaptainBlack
Re: Moment generating function for geometric
Quote:

Originally Posted by whiteboard
geometric distribution given by

$Pr(X=x) = (1/a)(1-(1/a)^{x-1})$ where a > 1.

Am I right in saying the distribution above is the same as

$Pr(X=x) = p(1-p)^{x-1}$ which is just the normal geometric pdf or does the change from p to 1/a change something else

What is raised to the power (x-1) in each of these cases? (and is it a typo?)

CB