random size particle system

is there a way to control the randomness of the objects created by an emitter?
It seems to me that it is possible to change only a single random size parameter (from 0 to 1) but it is not clear to me what does it mean and which kind of law is used to randomize. is there a possibility to specify the size distribution used, maybe with an add-on or a script?

Simple workaround is to use Group instead of Object. You make your own size distributed objects and group them all. And, emit that group with Random size set to zero. You will get somewhat the distribution you want; the object within the group is randomly selected still.