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Last updated: 08/12/2006

Methodological bases
Evaluation process (How?)
Intervention strategy


Intervention logic


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What is this?

All the activities and expected effects (outputs, results and impacts) of an intervention, as well as the assumptions that explain how the activities will lead to the effects in the context of the intervention.

The intervention logic may be "faithful" to the programming documents and to the documents establishing the policy to which the intervention is related. In this case, the expected effects are inferred from the stated objectives in the official documents.

When the intervention logic is reconstructed during the evaluation, implicitly expected effects that were not mentioned in the initial documents may be taken into account. The fact that this is no longer a "faithful logic" must then be mentioned. The "faithful" approach is relevant when the objectives are expressed precisely and in a verifiable way. The other option is preferable if objectives are too vague or ambiguous.

The intervention logic often evolves over time. In such cases, it is justified to reconstruct it several times, for successive periods.

The intervention logic is a useful simplification of reality, but one has to bear in mind the complexity of the real world. In addition to the reconstruction of the intervention logic, it is useful to identify the main external factors that condition or limit the implementation and effects. One also has to remember that real causal explanations are often more complex than initial assumptions.

What is the purpose?

  • To help to clarify the objectives and to translate them into a hierarchy of expected effects so that they can be evaluated.
  • To suggest evaluation questions about these effects.
  • To help to assess the internal coherence of the intervention.


How can it be reconstructed?

Collect and analyse reference documents:

  • Collect the official documents establishing the intervention and allocating resources.
  • Identify the main activities.
  • Identify the objectives.
  • Translate the objectives into expected results and impacts.
  • Connect the activities to the expected impacts by reconstructing the logical cause-and-effect relations (if… then…).
  • Check that cause-and-effect relation are logical, i.e. considered as plausible in the light of available knowledge.
  • Discuss the reconstructed logic with a few key informants (designers and managers) and with the experts of the policy domain/country concerned.
  • Present and discuss the intervention logic in a reference group meeting.


The most common presentations

Logical framework

This technique consists in producing a presentation in the form of a matrix that specifies the objectives (first column), how they should be verified (second column: indicators, and third column: sources), and the main assumptions on the external factors (fourth column).
The lines of the logical framework have a simplified presentation of the intervention logic, on only four rows: activities, results, purpose (i.e. direct benefit for the targeted group) and goal.
This representation is adequate for a simple intervention, like a project or well-targeted programme. However, it cannot fully grasp the complexity of a heterogeneous intervention such as an integrated rural development programme, a country strategy or support for a sector policy.
Due to its simplified nature, the logical framework allows for specifying the indicators that should be used at each row, as well as most external factors.

Objectives diagram

This technique consists in the identification of officially stated objectives and a graphical presentation of the logical relations between objectives, from the most operational to the most global. The intervention logic is represented in the form of boxes and arrows.
A particular form of representation is the objectives tree. It is applied in the case where each objective on a lower rank contributes towards a single objective on a higher rank.
Unlike the logical framework, the diagram can have as long chains of objectives as necessary. It can be used to highlight synergies and complex relations between objectives (except in the case of the objectives tree).
This representation is appropriate for complex interventions such as integrated programmes, country strategies or sector policies.

Diagram of expected effects

This technique is similar to the diagram of objectives since it also builds upon officially stated objectives. However, the objectives are translated into expected effects before being presented as a diagram. By translating objectives into expected effects, more concrete and easily verifiable concepts can be worked on.



  • Always re-examine the intervention logic. In the ideal world the intervention logic should be part of the intervention design and should be available at the time of the evaluation in the form of a framework or diagram. In the real world these points should be verified.
  • In the case of complex interventions (and especially country level evaluations), it is useful to produce several detailed diagrams and a synthesis diagram. A highly complex diagram cannot be used.
  • Beware of the risk of ex post rationalisation. To reduce this risk, clearly explain the reconstruction process and the options chosen.