Choice of a ‘Reality Index’ for Suspected Cyclic Variations

Abstract

THERE are natural phenomena which, without being purely periodical in character, show cyclic variations with maxima of different height, minima of different depth and varying intervals between consecutive maxima or minima. While in many cases the cyclic variations are so strongly marked that there can be no doubt as to their reality, in other cases it might be difficult to decide whether the variations appearing in a series of observed quantities are of real significance or not. In the latter cases it would be advantageous if we could find a ‘reality index’ which would indicate the degree of reality of suspected cyclic variations in a similar manner as, for example, in the calculus of correlation the correlation coefficient expresses the degree of relationship between two sets of observed quantities.