Sufficiency and conditionality

This is the authors' abstract. We don't add key points for this paper.

Ancillary statistics are divided into two logically diatinct types: those determined by the experimental design and those determined by the mathematical modelling of the problem. It ie pointed out that, in the class of inference problems where our purpose is to gain information or insight into the nature of a chance set-up, a weakened conditionality principle when applied first removes the possibility of deriving the likelihood principle. Since to some extent a conditionality principle must be applied in experiment definition, it is argued that this is a necessary first step if full acceptance of the likelihood axiom is to be avoided.