Random samples of count data can be tested to see if it is reasonable to assume the sampled population can be modeled with a Poisson distribution.

The test statistic for this test is a Chi-square statistic with (n-1) degrees of freedom.

Where n is the sample size (the number of c values),

s^{2} is the variance of the counts, and

is the average count.

This is a two-tailed test, with rejection occuring when the two-tailed chi-square probability is less than or equal to alpha.