This Monte Carlo randomization approach
redistributes cases of disease among spatially or temporally referenced
sub-groups using Poisson random variables. This approach is used in the
Score, Bithell
This method generates randomized case counts drawing from Poisson distributions.
The shape of the Poisson distribution depends on one parameter, 
(lambda), that is its mean and variance (see example Poisson
distributions below). In this case, is set using the
expected case count for that subgroup (region or time period), the product
of the population-at-risk and the average or user-specified baseline risk.
