138

G74

of Ss would be P, in case existing general conditions should undergo no alteration, then in case there be any definite reason to expect that of the Ss coming to our experience from a certain subclass, say the Ss that are Ts, a markedly different proportion will be P, from the proportion among experienced Ss that are not T, then our suitable method of forming the sample must insure that the proportion of Ss that are Ts shall be so nearly the same in the sample as it will be in our future experience, so long as