Psychometric analysis of Rosenberg's self-esteem scale by using methods of classical test theory (CTT) and item response theory (IRT)

Psychometric analysis of Rosenberg's self-esteem scale was conducted on the sample of 591 adolescents (234 mates, 357 females, mean age 18,77 years). Both classical test theory and item response theory methods were used to evaluate psychometric properties of the scale and its items. Similarly to several previous researches, factor analysis revealed two correlated factors with positively and negatively worded items. Classical item analysis confirmed that most of the items contributed well to internal consistency of the scale. Both CTT as well as IRT analysis using Samajima's graded response model showed that individual items differ in their discrimination and are differently related to the level of self-esteem. Information function of the scale also revealed that the scale is more informative in persons with low and middle level of self-esteem and less informative in persons with high level of self-esteem. Item analysis showed that coefficients from both approaches tended to converge.