# Probability using distribution(lambda)?

• May 17th 2011, 06:16 AM
Kimberly
Probability using distribution(lambda)?
Thank you for reading! In this exercise, I think the lambda sign threw me off.

Here's the problem:

The number of monthly repairs on a computer (I'm guessing it was a PC, lol!) is a random variable that has the distribution with $\displaystyle \lambda = 5.5$. Find the probability that the computer works for a month:

a) without need for repairs
b) with need of two repairs

Is it THIS formula? ==> $\displaystyle f(x,\lambda) = \frac{\lambda^x e^{-\lambda}}{x!}$

If so, what would $\displaystyle e$ be? I'm assuming that $\displaystyle \lambda$ is given (=5.5) and I'm guessing $\displaystyle x$ is the number of repairs needed on the computer (which would be $\displaystyle x!=0!$ on "a" and $\displaystyle x!=2!$ on "b").

Thank you for all your help!
• May 17th 2011, 06:35 AM
TheEmptySet
This is called the Poisson distribution!

See this link and then show us what you have tried.

Poisson distribution - Wikipedia, the free encyclopedia