Abstract
The Fourth Industrial Revolution (4IR) has led to the need for a redefinition of teacher effectiveness, particularly in science, technology, engineering, and mathematics (STEM) education areas such as chemistry. In the study reported on here I used a quantitative, exploratory cross-sectional survey design to validate the 4IR chemistry teachers' effectiveness scale (4IRCTES) using Mokken scale analysis (MSA) with the automated item selection procedure (AISP). The study population included chemistry teachers and senior secondary school students from public and private schools in Osun and Oyo States, Nigeria. Data were collected from 35 teachers and 320 students through multistage and proportionate stratified random sampling. The 4IRCTES, originally consisting of 49 items across 6 domains, underwent expert content validation. A pilot study involving 20 teachers and 50 students resulted in a Cronbach's alpha of 0.87, indicating strong internal consistency. The AISP analysis revealed 5 interpretable sub-scales, each representing a unidimensional construct, confirming the multidimensional structure of the 4IRCTES and supporting its construct validity and psychometric reliability. The findings show that the 4IRCTES is a reliable and valid tool for evaluating chemistry teacher effectiveness in technology-driven educational settings. This study emphasises the value of nonparametric item response theory methods like MSA in the validation of educational instruments and highlights the essential 4IR competencies needed for effective STEM teaching in Nigerian secondary schools.