What is the mean and the variance for geometric distribution?

Answer 1

http://mathworld.wolfram.com/GeometricDistribution.html

this site has a lot of very good information on the geometric distribution.

To derive and prove the solution you need to know this:

for any discrete random variable, X, you can find the mean by evaluating the sum
E(X) = μ = ∑ x * P(X = x)
over all possible values of X

the variance is found by:

Var(X) = σ² = ∑ (x - μ)² * P(X = x)
= ∑x² * P(X = x) - μ²

Answer 2

1/p and (1-p)/p^2