The PoissonDistribution defines the method:
/**
* Calculates the Poisson distribution function using a normal
* approximation. The {@code N(mean, sqrt(mean))} distribution is used
* to approximate the Poisson distribution. The computation uses
* "half-correction" (evaluating the normal distribution function at
* {@code x + 0.5}).
*
* @param x Upper bound, inclusive.
* @return the distribution function value calculated using a normal
* approximation.
*/
public double normalApproximateProbability(int x) {
// Calculate the probability using half-correction.
return normal.cumulativeProbability(x + 0.5);
}
This method does not seem to add value. A user would have to choose to use
it when they know the approximation is good, typically if the mean is
large. I would recommend removing it from the API.
Alex
