Development and Validation of a Deep Thai Language Proficiency Test for Lower Secondary School Students Using the Two-Parameter Logistic Item Response Theory Model (2PL-IRT)

Abstract

This study aimed to (1) develop and validate a deep Thai language proficiency test for lower secondary school students using the Two-Parameter Logistic Item Response Theory (2PL-IRT) model, and (2) propose guidelines for constructing and validating such a test appropriate to the Thai educational context. The study employed a research and development (R&D) design. The sample consisted of 250 lower secondary school students. The research instrument was a 30-item, four-option multiple-choice test. Data were analyzed using descriptive statistics and the Two-Parameter Logistic Item Response Theory (2PL-IRT) model. The findings revealed that (1) the developed test demonstrated acceptable content validity, with Item–Objective Congruence (IOC) values ranging from 0.60 to 1.00; (2) the response data fit the 2PL model well, with the test items showing good discrimination indices and difficulty parameters covering students with low, moderate, and high ability levels; (3) the test demonstrated high reliability (IRT reliability = 0.89) and measured students' abilities with high precision, particularly at the moderate to high ability levels; and (4) systematic guidelines for constructing and validating a deep Thai language proficiency test suitable for the Thai educational context were synthesized. The proposed guidelines emphasize construct definition, test development, and quality evaluation using the 2PL-IRT model and can serve as a framework for developing high-quality educational assessment instruments.