Binomial Distribution Homework: Equations and Solutions

[planauts]

Homework Statement

http://puu.sh/epl6
Answer
http://puu.sh/eplm

Homework Equations

The Attempt at a Solution

No clue on how to attempt this problem. Any help would be appreciated, thanks!

 

[Ray Vickson]

Homework Statement

http://puu.sh/epl6
Answer
http://puu.sh/eplm

Homework Equations

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