The core idea
A logic model sets out how an intervention is expected to work. Inputs are resources; activities are what is done; outputs are immediate deliverables; outcomes are changes in behaviour, capability or conditions; impact concerns wider or longer-term effects. Definitions can vary between evaluation traditions, so state how you use them. Add assumptions and external influences rather than drawing an apparently inevitable chain. A logic model supports evaluation design but does not itself demonstrate that a programme caused its outcomes.
Source and attribution [1]Using it in practice
Develop the model with people who deliver and experience the initiative. Start from the intended change and work backward to what would need to happen. Identify a small number of measures and a feasible way to collect them. Check that each activity has an owner and that the assumed resources exist. Use the model to decide what to investigate if the programme does not work as expected.
An example, not a reported case
Worked example · illustrative
An invented onboarding programme uses supervisor time and training materials as inputs. Activities include supported practice and check-ins. Outputs include completed sessions. Outcomes include demonstrated competence and clearer escalation. The hoped-for impact is more reliable service and sustainable retention. If attendance is high but competence does not improve, the evaluation examines practice quality rather than declaring success because every session ran.
What to watch for
Outputs and outcomes are often confused. A completed form is not necessarily changed behaviour. Linear sketches can hide feedback loops and conditions outside HR’s control. Do not force every initiative into a financial impact measure. Keep the model proportionate and update it when evidence shows that an assumption was wrong.
Make assumptions visible
Write a short sentence between each pair of stages: for example, staff can attend practice during paid time, supervisors provide usable feedback, and the task occurs often enough to retain the skill. Identify assumptions with weak evidence and decide how to test them.
Add process and outcome questions
Process questions ask whether the intended activity happened and reached the intended people. Outcome questions ask what changed. An intervention can fail because its theory is weak or because delivery was incomplete. Gathering both kinds of evidence helps distinguish these possibilities.
Choose a small measurement set
For each measure, record the definition, source, timing, owner and burden on participants. Include an unintended outcome, such as workload displaced to colleagues. Avoid collecting a large survey simply because it is available. Each item should help answer an evaluation question.
Use the model during delivery
Review the model at a planned checkpoint. Record changes to the programme and why they occurred. If the intervention changes substantially, be explicit about what version the evaluation covers. The diagram should remain a working explanation rather than a frozen bid document.
Take it into your next conversation
Three useful questions.
- Which decision will this analysis change?
- Are the population, denominator, time period and assumptions explicit?
- What alternative explanation or unintended effect must we check?
Related terms
Go to the evidence
Sources & attribution
[1] UK government: Creating a logic model for an intervention ↗
The core idea is an original summary of the cited work. Application notes, examples and sketches are our interpretations, not quotations or reproductions of the authors’ figures. Publisher records may require access to read the full original work.
Published 2026-09-20 · Reviewed 2026-09-20. Editorial approach