A linear combination of the E[X] of random variable X

57 Views Asked by At

I don't understand how to calculate the linear combination to find Y from X. Any help is appreciated. Thanks.

Suppose $Y = (3X − 2)^2$, and $E[X] = 2$, $var(X) = 5$. Find $E[Y ]$.

1

There are 1 best solutions below

0
On BEST ANSWER

The Comments of @HarryAlli and @copper.hat give very good clues.

I will show key clues for working a similar problem: finding $E(V),$ where $V = (3X + 1)^2.$

$$E(V) = E[(3X + 1)^2] = \cdots = 9E(X^2) + 6E(X) + 1.$$ You know $E(X)$ and need $E(X^2).$ For that, consider $$ 5 = Var(X) = E(X^2) - [E(X)]^2 = E(X^2) - 4.$$

Something similar works for your problem.