# poisson distribution

• Sep 6th 2009, 10:40 PM
HD09
poisson distribution
Is there an intuitive way to explain the forumla $\displaystyle P(X=x)=\frac{e^{-\mu}\mu^x}{x!}$ ?

For example in the binomial distribution with n trials & probability of sucess p you can see that to get r sucesses you must also have n-r failures and the trials are independent so this probability is p^r x (1-p)^n-r, and then you don't care about the order so that's where the n choose r comes in...

But is there a way to explain the poisson formula? Where did it come from?
• Sep 7th 2009, 02:40 AM
mr fantastic
Quote:

Originally Posted by HD09
Is there an intuitive way to explain the forumla $\displaystyle P(X=x)=\frac{e^{-\mu}\mu^x}{x!}$ ?

For example in the binomial distribution with n trials & probability of sucess p you can see that to get r sucesses you must also have n-r failures and the trials are independent so this probability is p^r x (1-p)^n-r, and then you don't care about the order so that's where the n choose r comes in...

But is there a way to explain the poisson formula? Where did it come from?

http://www.uoxray.uoregon.edu/ph353/...stribution.pdf