William Stephenson
The Play Theory of Mass Communication
(1987 edition)
(orig. 1967)
[10]
A METHODOLOGICAL ADVANCE
... For over a century social scientists have been concerned with the fundamental problem of what should be the basis of measurement in their science. In physics there are units of weight and length, time and mass, and these suffice for all measurements. In the social sciences, when these units cannot be used, recourse is made to other devices either of an ad hoc nature (different therefore in every study) or else systematically constructed, as scales of intelligence, attitudes... These scales are based on the large-sample theory and the Theory of Error... Psychologists understand this very well, for a branch of their work, called differential psychology, is fashioned upon this methodology. The principle is important: it supposes that if we wish to measure a person's intelligence (for example), a test is made and applied to a large sample of individuals from a parent population. According to the theory of errors, the scores gained by such a large sample, for a suitably constructed test, will tend to be normally distributed. The scores—whatever their units may be—can be transformed to standard scores, which are pure numbers whose mean for the test is 0 and whose standard deviation is 1.0. ...then, any test one cares to make for the parent population of individuals...can be systematically reduced to standard scores, the same pure numbers for everything so measured. ...
