DistributionFactory factory = DistributionFactory.newInstance();
PoissonDistribution pd = factory.createPoissonDistribution(mean);
if(isCumulative)
return UtilFns.validateNumber(pd.cumulativeProbability(x));
else
return UtilFns.validateNumber(pd.probability(x));
}
/**
* The skewness of a distribution
* @param args arguments