Evidence Synthesis

What is evidence synthesis?

Evidence synthesis is the systematic process of identifying, selecting, appraising, and integrating findings from multiple studies or data sources to build a comprehensive understanding of a specific program area, intervention approach, or development challenge. Unlike a traditional narrative literature review that may selectively cite sources, evidence synthesis follows explicit, reproducible methods to minimize bias and provide a reliable foundation for decision-making.

The term encompasses several related approaches, from comprehensive systematic reviews that rigorously appraise and synthesize all available evidence on a question, to lighter-weight evidence integration exercises that draw on program monitoring data, evaluation reports, and relevant research to inform adaptive management decisions. The common thread is the intentional, structured approach to bringing together multiple sources of information rather than relying on a single study or anecdotal experience.

Why It Matters

In an era of increasing donor demand for evidence-based practice, programs cannot justify their intervention choices based on intuition or isolated success stories alone. Evidence synthesis provides the rigorous foundation needed to answer critical questions: What interventions have worked in similar contexts? What are the common failure modes? What implementation conditions are necessary for success?

For impact evaluation and contribution analysis, evidence synthesis establishes the counterfactual baseline - what would have happened without your intervention, based on what similar programs achieved. It helps identify appropriate indicators by revealing which measures have proven predictive of outcomes in comparable settings.

Perhaps most critically, evidence synthesis supports adaptive management by creating a living knowledge base that program teams can consult when making mid-course corrections. Rather than treating each evaluation as a standalone exercise, evidence synthesis connects your program's findings to the broader field, enabling cumulative learning across interventions.

In Practice

Evidence synthesis appears in M&E work in several forms, ranging from formal systematic reviews to lighter-weight integration exercises:

Formal systematic reviews follow PRISMA or Campbell Collaboration standards, with explicit search strategies, inclusion/exclusion criteria, quality appraisal of studies, and often meta-analysis. These are common in health and education sectors where large bodies of research exist. A donor might commission a systematic review before approving a multi-million dollar program to ensure the proposed intervention has demonstrated effectiveness.

Rapid evidence assessments condense the systematic review process into 2-4 weeks, focusing on recent high-quality studies and prioritizing speed over comprehensiveness. These are practical for program design timelines where a full systematic review is not feasible but evidence-based justification is still required.

Program-specific synthesis draws on your own monitoring data, evaluation reports, and lessons learned across multiple projects or time periods. For example, an organization running 15 agricultural livelihoods programs might synthesize findings across all projects to identify which intervention components consistently predict improved food security outcomes. This internal evidence synthesis directly informs MEL plans and indicator selection for new programs.

Comparative analysis examines multiple similar programs to understand why outcomes differ. This might involve comparing implementation approaches, contextual factors, or beneficiary populations across 5-10 projects to identify the conditions under which specific interventions succeed or fail.

The key is matching the synthesis approach to your decision context: a formal systematic review for major program design decisions, lighter-weight synthesis for adaptive management, and ongoing knowledge management practices to accumulate evidence over time.