# Poisson Distribution

timmyc
I need to fit a Poisson distribution to this set of data (no. of counts of radioactive decay)

The number of counts in a fixed time interval was recorded 500 times.

With the number of counts going from 0 - 9 respectively

39
106
130
100
67
34
15
7
1
1

I understand how to use the formula in simple probability situations but am a little stuck with this one.

I know the mean = the variance and worked that out to be 67.1 but when using this in the formlua I calculated explodes (shows math error).

Can someone help me please?

## Answers and Replies

Science Advisor
How did you get 67.1? Off hand (without doing the arithmetic) the mean looks like it should be around 2+.

(39x0 + 106x1 + 130x2 + ..... + 1x9)/500