Binomial Distribution

[planauts]

1. The problem statement, all variables and given/known data
http://puu.sh/epl6
Answer
http://puu.sh/eplm


2. Relevant equations



3. The attempt at a solution
No clue on how to attempt this problem. Any help would be appreciated, thanks!

[Ray Vickson]

1. The problem statement, all variables and given/known data
http://puu.sh/epl6
Answer
http://puu.sh/eplm


2. Relevant equations



3. The attempt at a solution
No clue on how to attempt this problem. Any help would be appreciated, thanks!

(a) What is the formula for f(k) \equiv \Pr\{X = k|X \geq 2 \}, for k = 2, 3, ...,n? Then E(X | X \geq 2) = \sum_{k=2}^n k f(k), and you ought to be able to get the cited formula from this.
(b) What is the formula for σ in terms of n and p? Look at it carefully.

RGV