An illustration of issues in factor extraction and identification of dimensionality in psychological assessment data.

Structural validity has long been regarded as critical to psychological measurement. However, in practical application, issues central to structural validity are often neglected. The purpose of this study was to illustrate the importance of several crucial choices that face researchers attempting to evaluate the structure of data from a given scale. In this study, I compared the structural solutions derived via principal components analysis and principal axis factoring using eigenvalues, scree plots, and traditional parallel analyses with data from the Purpose in Life Test (Crumbaugh & Maholick, 1964). I discuss the importance of structural validity for overall construct validity and the importance of carefully considering factor analytic methodology. I provide recommendations for uses of factor analysis.