Abstract
{ "background": "Community health centres are critical nodes in sub-Saharan African health systems, yet robust methodologies for evaluating their operational reliability are underdeveloped. Existing assessments often lack rigorous causal designs, limiting actionable insights for system strengthening.", "purpose and objectives": "This study aimed to appraise a quasi-experimental design for measuring system reliability in Tanzanian community health centres. Its primary objective was to estimate the causal effect of a structured logistical intervention on facility-level operational consistency.", "methodology": "We employed a difference-in-differences design, comparing 30 intervention facilities receiving a targeted supply-chain module with 30 matched control facilities over an observation period. System reliability was operationalised as the weekly coefficient of variation in the availability of 15 essential medicines. The core statistical model was $Y{it} = \\beta0 + \\beta1 (\\text{Treat}i \\times \\text{Post}t) + \\gammai + \\deltat + \\epsilon{it}$, where $\\gammai$ and $\\deltat$ are facility and time fixed effects, with inference based on cluster-robust standard errors.", "findings": "The intervention significantly reduced the mean coefficient of variation by 18.2 percentage points (95% CI: -27.1, -9.3). This indicates a substantial improvement in the consistency of medicine availability. The parallel trends assumption, tested via event-study analysis, was not violated.", "conclusion": "The applied quasi-experimental design proved methodologically sound for isolating the effect of a system-strengthening intervention on operational reliability. The significant reduction in supply variability demonstrates the potential of targeted logistical support.", "recommendations": "Programme implementers should adopt similar quasi-experimental frameworks for evaluating health system interventions. Policymakers should consider scaling the tested logistical module, with adaptations informed by the methodological insights on reliability measurement.", "key words": "health systems research, quasi-experimental design, operational reliability, essential medicines, sub-Saharan Africa, difference-in-d