# expected and variance

• July 9th 2007, 10:25 AM
harry
expected and variance
Expectation and variance of random variable
• July 9th 2007, 12:36 PM
ThePerfectHacker
1)To find the expected value simply find $\sum xp(x)$

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

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