# Math Help - true or false???

1. ## true or false???

if x distributed as Poisson distribution with parameter lambda=5 find:

1- moment generating function of (3x-2)
2- the mean and variance of (-4x-6)
3- the moment generating function about the origin

solutions :
(1) {e ^(-2t)} * {e^((5e^3t)-5)}

(2) mean = -26 & variance = 80

(3) 30

2. Originally Posted by flower3
if x distributed as Poisson distribution with parameter lambda=5 find:

1- moment generating function of (3x-2)
2- the mean and variance of (-4x-6)
3- the moment generating function about the origin

solutions :
(1) {e ^(-2t)} * {e^((5e^3t)-5)} Mr F says: Correct, since if X has moment generating function m(t) then (it can be easily shown that) aX + b has moment generating function ${\color{red} e^{bt} \, m(at)}$. And you have m(t) from question 3.

(2) mean = -26 & variance = 80 Mr F says: Correct, since E(-4X - 6) = -4 E(X) - 6 and Var(-4X - 6) = 16 Var(X).

(3) 30 Mr F says: Wrong. ${\color{red}m(t) = e^{5(e^t - 1)}}$.
The proof of the result given in (3) can be found in this thread: http://www.mathhelpforum.com/math-he...tribution.html

3. thank you >>>

(3) the second moment about the origin " my question is false but my answer i think true "
= 30