Fig . 9.—Diagram to show the standing of children in a single class in a New York City school, in respect to their ability in arithmetic. There are wide divergences in the scores they made.
The literature of experimental psychology and anthropology is crammed with such examples as the above. No matter what trait of the individual be chosen, results are analogous. If one takes the simplest traits, to eliminate the most chances for confusion, one finds the same conditions