An overview of the Normal Ogive Harmonic Analysis Robust Method (NOHARM) approach to item response theory

Abstract

Here we provide a description of the IRT estimation method known as Normal Ogive Harmonic Analysis Ro- bustMethod (NOHARM). Although in someways this method has been superseded by new computer programs that also adopt a specifically factor-analytic approach, its fundamental principles remain useful in certain applications, which in- clude calculating the residual covariance matrix and rescaling the distribution of the common factor (latent trait). These principles can be applied to parameter estimates obtained by any method.