Probability Question

Question

X has the following pdf

 

x       p(x)

-----|-------

 10  |0.40

 15  |0.15

 17  |0.20

 21  |0.15

 22  |0.10

 

a)What is the moment generating function for X

b)Use your Moment Generating function to determine E[X]

 

I know how to do part a.

Im very confused with part b of the problem!! 

Answer 1

If you have M(t) (the MGF of x) all you need to do is find the derivative evaluated at t=0: M'(0)=E(x).

 

Let me know if that works.