Abstract
OBJECTIVE: To validate the Workplace COVID-19 Knowledge and Stigma Scale (WoCKSS) using item response theory (IRT), exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). DESIGN: Cross-sectional psychometric validation. SETTING: Manufacturing companies registered in Malaysia. PARTICIPANTS: A total of 137 factory workers participated in the exploratory phase and 300 in the confirmatory phase. Inclusion criteria were Malaysian nationality and ability to read Malay. METHODS: The knowledge domain was examined using the two-parameter logistic IRT model in two stages: an exploratory IRT analysis in phase 1 to screen items and a confirmatory IRT analysis in phase 2 to evaluate the final item set. The stigma domain was analysed using EFA followed by CFA. Reliability was assessed using Cronbach's alpha and McDonald's omega (ω). The development process and content and face validity results were previously published. RESULTS: 14 knowledge items were retained after exploratory IRT and formed the final knowledge scale evaluated in confirmatory IRT. For these final items, discrimination parameters ranged from 0.77 to 3.17 and difficulty values from -4.47 to 0.23, with unidimensionality supported (p=0.644). EFA supported a three-factor stigma structure (stereotype, fear, prejudice), and CFA confirmed excellent model fit (χ(2)=8.91, df=11, p=0.630; root mean square error of approximation=0.00; Comparative Fit Index=1.00; Tucker-Lewis Index=1.00; standardised root mean square residual=0.021). Composite reliability by McDonald's omega ranged from 0.691 to 0.893. CONCLUSION: WoCKSS is a reliable and valid instrument for assessing workplace COVID-19 knowledge and stigma in industrial sectors in Malaysia.