Irrationality refers to human thoughts and beliefs that signify lack of rationality and entail erroneous perceptions about situational, personal, or collective idiosyncrasies, while it is independent of one's intellectual ability. Irrational beliefs are ubiquitous in all social and cultural groups and attract a special interest in behavioral sciences, where the primary concern is the development of instruments for identifying and measuring them. The present study evaluates the psychometric properties of Greek version of Teachers' Irrational Belief Scale (TIBS-G), a 25-item self-reported instrument using data collected from 835 participants. The exploratory procedure, implementing scree plot with parallel analysis, demonstrated the dimensionality of four factors, namely: Self-downing (SD), Authoritarianism (A), Demands for Justice (DJ), and Low Frustration Tolerance (LT). The corresponding reliability measures using Cronbach's alpha and McDonald's omega were ranged between 0.70 and 0.80. Subsequently, confirmatory factor analysis showed an adequate fit of the measurement model [χ2 = 579.98, df = 183, p < 0.001; CFI = 0.960; TLI = 0.956; RMSEA = 0.051]. In addition, measurement invariance was performed, which demonstrated differences between genders. Finally, discussion on the importance of irrational beliefs and the possible implementation of the TIBS instrument in educational research is provided.
Keywords: irrational beliefs; measurement invariance; psychometric properties.