The Upper and Lower Twenty-Seven Per Cent Rule

1 September 1957

journal article
Published by Cambridge University Press (CUP) in Psychometrika

Vol. 22 (3) , 293-296
https://doi.org/10.1007/bf02289130

Abstract

A simplified re-derivation of the formula underlying the rule is presented, followed by a derivation of the comparable rule for the unitrectangular distribution, which turns out to be a 33-per cent rule. Critical comments are offered concerning two assumptions: normality of the score distribution and equality of mean standard errors of measurement in the high and low groups.

Keywords

STANDARD ERROR
PUBLIC POLICY
STATISTICAL THEORY
CRITICAL COMMENT
SCORE DISTRIBUTION

This publication has 2 references indexed in Scilit:

The Relation of Test Score to the Trait Underlying the Test
Educational and Psychological Measurement, 1953
The selection of upper and lower groups for the validation of test items.
Journal of Educational Psychology, 1939