On the Use and Interpretation of Certain Test Criteria for Purposes of Statistical Inference

In an earlier paper* we have endeavoured to emphasise the importance of placing in a logical sequence the stages of reasoning adopted in the solution of certain statistical problems, which may be termed problems of inference. In testing whether a given sample, Z, is likely to have been drawn from a population H, we have started from the simple principle that appears to be used in the judgments of ordinary life-that the degree of confidence placed in an hypothesis depends upon the relative probability or improbability of alternative hypotheses. From this point of view any criterion which is to assist in scaling the degree of confidence with which we accept or reject the hypothesis that X has been randomly drawn from HI should be one which decreases as the probability (defined in some definite manner) of alternative hypotheses becomes relatively greater. Now it is of course impossible in practice to scale the confidence with which we form a judgment with any single numerical criterion, partly because there will nearly always be present certain a priori conditions and limitations which cannot be expressed in exact terms. Yet though it may be irmpossible to bring the ideal situation into agreement with the real, some form of numerical measure is essential as a guide and control. In our previous paper we have made use of the criterion of likelihood. That there may be other forms of criteria or that this one can be interpreted in a different manner is very possible, but our object has been to find a single principle connecting the various sampling tests already in use, and one which could be extended to new problems.