what is variance in poisson dist
The above plot illustrates Poisson probabilities for Î» = 7.5. and this plot illustrates Poisson probabilities for Î» = 15. The mean of the Poisson distribution is Î». For the Poisson distribution, the variance, Î», is the same as the mean, so the standard deviation is âÎ». Empirical tests. There are also some empirical ways of checking for a Poisson distribution. 1  The simplest and handiest way is to see if the variance is roughly equal to the mean for your Poisson data.