Chi-Square Test

["MacLellan, Jay A" <jay.a.maclellan@pnl.gov>]

Chi-square= (n-1)s^2/sigma^2, or 

s^2/(sigma^2)=(Chi-square)/(n-1)

Assuming the population is Poisson distributed the variance equals the mean, and

s^2/mean=Chi-square/(n-1)

The chi-square values for 10 counts (nine degrees of freedom) are:

2.088 (1%)
2.700 (2.5%)
3.325 (5%)
4.168 (10%)
8.343 (50%)
14.684 (10%)
16.919 (95%)
19.023 (97.5%)
21.666 (99%)

If you want a 5% total confidence interval choose 2.7/9 and 19.023/9 as your
acceptance criteria.  Accept the hypothesis that the measurements are Poisson
distributed if the ratio of the calculated variance to the mean is between 0.3
and 2.11.

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