Physical Interpretation of the Multiparticle Generating Functional and Partition Function

It is shown that the multiparticle generating functional and the multiplicity generating function (or partition function) are experimental observables and can be measured directly for finite ranges of their parameters. Their derivatives can also be measured directly. Since these functions are observables, they are subject to statistical fluctuations due to the necessarily finite number of measurable events used in their evaluation. The expected RMS fluctuations of the partition function are shown to be simply expressed in terms of the total number of events and the partition function itself. Examples are given to clarify these results and their physical interpretation.