{ "background": "Manufacturing productivity in developing economies is critical for industrial growth, yet robust empirical evaluation of operational interventions remains scarce. This case study addresses the need for rigorous, quasi-experimental analysis within industrial engineering contexts.", "purpose and objectives": "This study aims to methodologically evaluate the application of a difference-in-differences (DiD) model to quantify yield improvement following a systematic process optimisation intervention in a manufacturing setting. It seeks to demonstrate the model's utility for isolating causal effects amidst typical production variability.", "methodology": "A quasi-experimental case study was conducted using panel data from multiple production lines. The core econometric model is specified as $Y{it} = \\beta0 + \\beta1 \\text{Treat}i + \\beta2 \\text{Post}t + \\delta (\\text{Treat}i \\cdot \\text{Post}t) + \\epsilon_{it}$, where $\\delta$ is the DiD estimator. Inference is based on cluster-robust standard errors at the production-line level.", "findings": "The DiD estimator revealed a statistically significant positive treatment effect. The intervention increased average production yield by 7.3 percentage points (95% CI: 5.1 to 9.5). This result was robust to several sensitivity checks, confirming the efficacy of the implemented engineering modifications.", "conclusion": "The difference-in-differences framework provides a powerful and credible methodological approach for evaluating engineering interventions in manufacturing, effectively controlling for unobserved time-invariant confounders and common temporal trends.", "recommendations": "Manufacturing engineers and plant managers should adopt quasi-experimental evaluation designs like DiD for assessing process changes. Future research should integrate real-time sensor data into such models for enhanced granularity.", "key words": "difference-in-differences, causal inference, manufacturing yield, process optimisation, quasi-experimental design, industrial engineering", "contribution statement": "This case study provides a novel, rigorous template