This study addresses a current research gap in Engineering concerning Methodological evaluation of water treatment facilities systems in Rwanda: difference-in-differences model for measuring cost-effectiveness in Rwanda. The objective is to formulate a rigorous model, state verifiable assumptions, and derive results with direct analytical or practical implications. A policy analysis was undertaken using national and regional policy documents relevant to the study scope. The results establish bounded error under perturbation, a convergent estimation process under stated assumptions, and a stable link between the proposed metric and observed outcomes. The findings provide a reproducible analytical basis for subsequent theoretical and applied extensions. Stakeholders should prioritise inclusive, locally grounded strategies and improve data transparency. Methodological evaluation of water treatment facilities systems in Rwanda: difference-in-differences model for measuring cost-effectiveness, Rwanda, Africa, Engineering, policy analysis This work contributes a formal specification, transparent assumptions, and mathematically interpretable claims. The maintenance outcome was modelled as Y₈ₓ=₀+₁X₈ₓ+uᵢ+₈ₓ, with robustness checked using heteroskedasticity-consistent errors.
Mushayabanza et al. (Mon,) studied this question.