ABSTRACT
A design of experiments (a prescription of what the physicists call a “crucial experiment”) is an essential appendix to any quantitative theory. And we usually have some such experiments in mind when we construct the theories, although – unfortunately – most economists do not describe their designs of experiments explicitly. If they did, they would see that the experiments they have in mind may be grouped into two different classes, namely, (1) experiments that we should like to make to see if certain real economic phenomena – when artificially isolated from “other influences” – would verify certain hypotheses, and (2) the stream of experiments that Nature is steadily turning out from her own enormous laboratory, and which we merely watch as passive observers.
