Expectation and variance of random variable

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- Jul 9th 2007, 10:25 AMharryexpected and variance
Expectation and variance of random variable

- Jul 9th 2007, 12:36 PMThePerfectHacker
1)To find the expected value simply find $\displaystyle \sum xp(x)$

2)Not sure how to find the Variance. - Jul 9th 2007, 12:53 PMPlato
Expected value: $\displaystyle E(X) = \sum\limits_{x \in X} {xP(x)} $.

Variance: $\displaystyle V(X) = E\left( {X^2 } \right) - \left[ {E(X)} \right]^2 = \sum\limits_{x \in X} {x^2 P(x)} - \left[ {E(X)} \right]^2 $