Adding Two Standard Deviations Together.

[pakuru]

I have a math problem that involves rolling two dice. To find out the standard deviation, i need to find the probablies, muu, and standard devations of rolling one dice, then use the formula Y=X+X, where X is the single dice roll, and Y is the value of two seperate die rolls. I can't figure out how i'm supposed to go about this problem when trying to find Y's Standard Deviation. Can anyone give me a few pointers? tricky AP stats!

 

[Unco]

X: the number to show up on dice roll
Y: the sum of the numbers to show up on two dice rolls

If necessary, draw up a probability distribution for X and X² to find E(X) and E(X²).

From there, Var(X) = E(X²) - [E(X)]²

And we can add variances.