{ "background": "Evaluating the operational efficiency of water treatment infrastructure in developing nations is critical for resource allocation and sustainable development. Traditional single-level regression models often fail to account for the hierarchical structure of facility data, such as plants nested within districts and regions, potentially leading to biased inferences.", "purpose and objectives": "This case study presents a methodological framework for applying multilevel regression modelling to assess efficiency gains in water treatment systems. Its objective is to demonstrate the model's superiority in quantifying the variance in efficiency attributable to different organisational levels and identifying key predictive factors.", "methodology": "We employed a three-level linear mixed-effects model. The core statistical model is $y{ijk} = \\beta0 + \\beta X{ijk} + u{k} + v{jk} + \\epsilon{ijk}$, where $y{ijk}$ is the efficiency score for plant $i$ in district $j$ and region $k$, $X$ represents plant-level covariates, and $uk$, $v{jk}$, and $\\epsilon{ijk}$ are independent random effects. Analysis used restricted maximum likelihood estimation with robust standard errors.", "findings": "The analysis quantified that approximately 22% of the total variance in efficiency scores was attributable to regional-level effects. A key concrete result is that a one-unit increase in normalised chemical dosing accuracy was associated with a 0.15 increase in the plant efficiency score (95% CI: 0.11 to 0.19), holding other factors constant.", "conclusion": "Multilevel regression provides a statistically rigorous and structurally appropriate method for analysing hierarchically nested engineering performance data, offering insights obscured by conventional regression techniques.", "recommendations": "We recommend that infrastructure efficiency audits adopt multilevel modelling as a standard analytical tool. Furthermore, policy interventions should be tailored to address specific inefficiencies identified at the regional and district levels, rather than applying uniform national strategies.", "key words": "multilevel modelling, hierarchical linear model, infrastructure efficiency, water treatment,