Scaling Subjective Variables by SPC (Sequential Pair Comparisons)

Abstract

Shapiro (1961) devised a scaling method based on pair comparisons to overcome the problems associated with numerical rating scales. Phillips (1963, 1966, 1970, 1977, 1979) developed the theory underlying Shapiro's method and extended it to increase the precision of measurement. In this paper we present a simpler justification of the Shapiro–Phillips method and propose improvements by sequentializing the presentation of pair comparisons. In this way, the total number of comparisons can be reduced to correspond with an acceptable level of reliability. Responses are recorded graphically producing an instant score and reliability check. Some possible generalizations are discussed.