The Estimation of the Discriminal Dispersion in the Method of Successive Intervals
- 1 December 1955
- journal article
- Published by Cambridge University Press (CUP) in Psychometrika
- Vol. 20 (4) , 299-305
- https://doi.org/10.1007/bf02289036
Abstract
A new algebraic formula is derived for estimation of the discriminal dispersion in the method of successive intervals. The legitimate use of the formula requires that as many normal deviates as possible be present in the matrix. For this reason, it is recommended that deviates corresponding to the interval (0.01, 0.99) of the cumulative proportions be used, instead of those corresponding to (0.05, 0.95), the interval used by Edwards and Thurstone. Computations on data published by Edwards and Thurstone showed that when adjustment was made for variability in dispersions calculated by the formula of this paper, a reduction of fifty per cent in mean absolute discrepancy was produced. Since the formula is easy to use and avoids the disadvantages of its predecessors, it should have fairly wide applicability in psychological research.Keywords
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