Development and psychometric validation of the Food Safety Practice Scale (FSPS-18) for the adult population in Bangladesh: insights from the classical test theory and gender invariance test in a cross-sectional study

Background: Food safety practices contribute as a primary factor to foodborne diseases and deaths, though there is no validated known psychometric properties scale accessible for consistent measurement. Aim: The current study aims to develop and validate the psychometric properties of the multifactorial Food Safety Practice Scale. Method: for scale development. We developed a structured questionnaire using a deductive approach based on the WHO's Five Keys to Safer Food's domains, checked content validity, pre-tested and included 1652 responses (mean age: 30.79 years) using convenience sampling in a cross-sectional study. Descriptive statistics were calculated. Next, the dataset was split into two independent subsets. Item reduction and factor extraction were conducted on the Exploratory Factor Analysis (EFA) subset, while the scale's dimensionality, reliability and validity were tested on the Confirmatory Factor Analysis (CFA) subset. Result: The final scale, FSPS-18, comprised 18 items, refined from an initial pool of 31 items, grouped into four highly correlated constructs, with inter-construct correlations ranging from 0.68 to 0.83. Factor loadings were substantial in both EFA and CFA (0.536 to 0.929). The scale demonstrated robust reliability in both datasets (Cronbach's alpha ≈ 0.93). CFA indices indicated excellent model fit. Additionally, the invariance test, convergent, discriminant and concurrent validity were well demonstrated. Although we rooted our conceptual framework in WHO's domains, our scale demonstrated four factors that are different from the concept. However, FSPS-18 factors are easily interpretable using the Theory of Planned Behavior model and Health Belief Model. Conclusion: The FSPS-18 has proven to be a reliable and valid scale, contributing to the standardisation of measuring food safety practices.