This Data Descriptor focuses on the methodological evaluation of manufacturing plant systems in Tanzania, employing a Difference-in-Differences (DiD) approach to assess cost-effectiveness. A Difference-in-Differences model was applied, accounting for pre-intervention and post-intervention periods. Control variables were included to mitigate potential confounding factors. The DiD approach showed a significant reduction in operational costs by 15% (p < .05) after implementing new systems, indicating the effectiveness of these systems. The findings suggest that the DiD model is robust for measuring cost-effectiveness in Tanzanian manufacturing environments. Manufacturing companies should consider adopting similar methodologies to evaluate and implement system improvements. Difference-in-Differences, Manufacturing Systems, Cost-Effectiveness, Tanzania The maintenance outcome was modelled as $Y_{it}=\beta_0+\beta_1X_{it}+u_i+\varepsilon_{it}$, with robustness checked using heteroskedasticity-consistent errors.