Two Random Variables

[WeeG]

Hi,

I got a very easy multiple question, I think that the correct answer is missing, please verify...

Two independent random variables are given, X1 and X2. The variance of X1 is 1, and the variance of X2 is 4. What is the variance of (X1+2X2) ?

a. 22
b. 9
c. 2
d. sqrt(3)
e. impossible to know

what I did is:
Var(X1+2X2)=Var(X1)+4Var(X2)=1+4*4=17

cheers !

[Dragan]

Hi,

I got a very easy multiple question, I think that the correct answer is missing, please verify...

Two independent random variables are given, X1 and X2. The variance of X1 is 1, and the variance of X2 is 4. What is the variance of (X1+2X2) ?

a. 22
b. 9
c. 2
d. sqrt(3)
e. impossible to know

what I did is:
Var(X1+2X2)=Var(X1)+4Var(X2)=1+4*4=17

cheers !

I can verify that your answer is correct - given the question you've posed.