{ "background": "The reliability of manufacturing systems is a critical determinant of industrial productivity and economic development. In many developing economies, systematic evaluations of these systems, particularly within operational plants, are scarce, leading to a lack of context-specific empirical evidence for improvement.", "purpose and objectives": "This study aims to methodologically evaluate the reliability of manufacturing systems within operational plants and to develop a robust analytical model for identifying the key operational and organisational factors influencing system reliability.", "methodology": "A cross-sectional field study was conducted across multiple manufacturing plants. Data were collected on system failures, maintenance logs, and operational parameters. A two-level hierarchical linear model was employed, with equipment nested within production lines. The core model is specified as $\\log(MTBF{ij}) = \\beta{0j} + \\beta{1}X{ij} + \\epsilon{ij}$, where $\\beta{0j} = \\gamma{00} + \\gamma{01}Z{j} + u{0j}$. Analyses used robust standard errors to account for heteroscedasticity.", "findings": "The multilevel regression revealed that preventive maintenance adherence at the line level was a significant predictor of mean time between failures (MTBF). A one-standard-deviation increase in preventive maintenance compliance was associated with a 24% increase in MTBF (95% CI: 18% to 30%). Variability in reliability was substantially greater between production lines than within them.", "conclusion": "The methodological approach confirms that manufacturing system reliability is influenced by factors operating at different organisational levels. The findings underscore the disproportionate impact of line-level management practices over equipment-specific variables in this context.", "recommendations": "Manufacturing managers should prioritise and rigorously enforce scheduled preventive maintenance protocols at the production line level. Further research should integrate real-time sensor data into the proposed multilevel modelling framework.", "key words": "system reliability, hierarchical linear modelling, preventive maintenance, manufacturing, industrial engineering", "contribution statement": "This