Exact Probability

1. Mar 8, 2008

kuahji

Hoping this will be my last stats question for awhile.

X is the random variable for the sum obtained by rolling two fair dice.

I figured out the mean & variance which are 7 & 35/6.

But I then get the question part A) "Use Chebyshev's Theorem to find the lower bound for the probability that a value X is within two standard deviations of the mean X." Which I computed to be 3/4.
Part B) of that question says "Determine the exact probability that this sum is within the same two standard deviations."
Here I'm kinda lost. I recall in class, I think the answer was 34/36, but the professor didn't elaborate.