Improvement of Test Criteria

Perhaps no other science is as conscious of validity coefficients as psychology. This may be partly due to the impetus given statistical methods by such early investigators as Galton, Pearson, Yule, and Spearman. Later work by Thurstone, Fisher, Holzinger, Garret and others has kept the profession highly conscious of the need for refined and, in some instances, involved statistical evaluation. In certain types of experimental work, such as mental testing, it is highly essential to keep the validity of tests high. It is, of course, taken for granted that in any science accurate measuring instruments are available for use without elaborate standardization. It should be unnecessary to spend time in making two or three hundred measurements with a high grade scale to be sure of the accuracy. Instead, a single test weight is used to check the accuracy of the instrument