- #1

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We define Y = sum from j=1 to 15(j*Xj)

whats is the variance VAR(Y)=?

i will find this with VAR(Y)=E(X^2)-(E(X)^2) but how i can find them?

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- Thread starter ParisSpart
- Start date

- #1

- 129

- 0

We define Y = sum from j=1 to 15(j*Xj)

whats is the variance VAR(Y)=?

i will find this with VAR(Y)=E(X^2)-(E(X)^2) but how i can find them?

- #2

Mark44

Mentor

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Your book probably has some theorems that cover finding the variance of a sum of multiple of random variables, such as the following.

We define Y = sum from j=1 to 15(j*Xj)

whats is the variance VAR(Y)=?

i will find this with VAR(Y)=E(X^2)-(E(X)^2) but how i can find them?

If X and Y are random variables, and a and b are constants, then

1. Var(X + Y) = Var(X) + Var(Y) + 2Covar(X, Y)

2. Var(aX) = a

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