# Expected Value Problem

• Nov 2nd 2008, 01:51 PM
HardyHar
Expected Value Problem
You order twelve burritos from a Mexican restaurant, five with hot peppers and seven without. However, the restaurant forgot to label them. If you pick three burritos at random, find the probability of the event:

(a) At most one has hot peppers

I honestly have no idea where to begin, and I do not find the chapter very helpful to me. Anyone have any hints or suggestions?
• Nov 2nd 2008, 04:39 PM
mr fantastic
Quote:

Originally Posted by HardyHar
You order twelve burritos from a Mexican restaurant, five with hot peppers and seven without. However, the restaurant forgot to label them. If you pick three burritos at random, find the probability of the event:

(a) At most one has hot peppers

I honestly have no idea where to begin, and I do not find the chapter very helpful to me. Anyone have any hints or suggestions?

Let X be the random variable number of hot pepper burritos.

$\displaystyle \Pr(X \leq 1) = \Pr(X = 0) + \Pr(X = 1)$.

Note: $\displaystyle \Pr(X = x) = \frac{{5 \choose x} \cdot {7 \choose 3 - x}}{{12 \choose 3}}$. Think about this.

X follows a hypergeometric distribution: Hypergeometric distribution - Wikipedia, the free encyclopedia