  We present a new method of calculating the distribution function and
fluctuations for a Bose-Einstein condensate (BEC) of N interacting atoms. The
present formulation combines our previous master equation and canonical
ensemble quasiparticle techniques. It is applicable both for ideal and
interacting Bogoliubov BEC and yields remarkable accuracy at all temperatures.
For the interacting gas of 200 bosons in a box we plot the temperature
dependence of the first four central moments of the condensate particle number
and compare the results with the ideal gas. For the interacting mesoscopic BEC,
as with the ideal gas, we find a smooth transition for the condensate particle
number as we pass through the critical temperature.
