A comparison of two approaches to correction of restriction of range in correlation analysis

A common problem in predictive validity studies in the educational and psychological fields, e.g. in educational and employment selection, is restriction in range of the predictor variables. There are several methods for correcting correlations for restriction of range. The aim of this paper was to examine the usefulness of two approaches to correcting for range restriction; Thorndike’s case 2 correction and ML estimates obtained from the EM algorithm, by comparing the corrected correlations with the correlation from an unrestricted sample. The unrestricted sample consisted of examinees who took the practical Swedish driving-license test regardless of their result on the theory test. Examinees that passed the theory test and took the practical test were regarded as a restricted sample. The result provided empirical support for the appropriateness of Thorndike’s case 2 correction method. Although using the EM algorithm yielded a good estimate of the correlation in the unrestricted sample, further studies are needed on this topic.