For several decades, the three-parameter logistic model (3PLM) has been the dominant choice for practitioners in the field of educational measurement for modeling examinee's response data from multiple-choice (MC) items. Past studies, however, have pointed out that the c-parameter of 3PLM should not be interpreted as a guessing parameter. This study found logical, empirical evidence showing that neither the a-, b-, or c-parameters of 3PLM can accurately reflect the discrimination, difficulty, and guessing properties of an item, respectively. This study reconceptualized the problem-solving and guessing processes with a modification of the 3PLM that eliminates ambiguity in modeling the guessing process. A series of studies using various real and simulated data demonstrated that the suggested model, in which the c-parameters were fixed at a computed probability for successful random guessing (i.e., c = 1 / k with k being the number of options), could provide a more feasible, stable, and accurate item estimation solution without sacrificing the model fit compared with a typical 3PLM. Accessed 13,077 times on https://pareonline.net from January 09, 2012 to December 31, 2019. For downloads from January 1, 2020 forward, please click on the PlumX Metrics link to the right.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Han, Kyung T.
"Fixing the c Parameter in the Three-Parameter Logistic Model,"
Practical Assessment, Research, and Evaluation: Vol. 17
, Article 1.
Available at: https://scholarworks.umass.edu/pare/vol17/iss1/1