sustainability Article An Item Response Theory to Analyze the Psychological Impacts of Rail-Transport Delay Mahdi Rezapour 1,*, Kelly Cuccolo 2, Christopher Veenstra 2 and F. Richard Ferraro 2 1 Wyoming Technology Transfer Center, University of Wyoming, Laramie, WY 82071, USA 2 Department of Psychology, University of North Dakota, Grand Forks, ND 58201, USA;
[email protected] (K.C.);
[email protected] (C.V.);
[email protected] (F.R.F.) * Correspondence:
[email protected] Abstract: Questionnaire instruments have been used extensively by researchers in the literature review for evaluation of various aspects of public transportation. Important implications have been derived from those instruments to improve various aspects of the transport. However, it is important that instruments, which are designed to measure various stimuli, meet criteria of reliability to reflect a real impact of the stressors. Particularly, given the diverse range of commuter characteristics considered in this study, it is necessary to ensure that instruments are reliable and accurate. This can be achieved by finding the relationship between the item’s properties and the underlying unobserved trait, being measured. The item response theory (IRT) refers to measurement of an instrument’s reliability by examining the relationship between the unobserved trait and various observed items. In this study, to determine if our instrument suffers from any potentially associated problems, the IRT analysis was conducted. The analysis was employed based on the graded response model (GRM) due to the ordinal nature of the data. Various aspects of the instruments, such as discriminability and informativity of the items were tested. For instance, it was found while the classical test theory Citation: Rezapour, M.; Cuccolo, K.; (CTT) confirm the reliability of the instrument, IRT highlight some concerns regarding the instrument.