Section 2: Describing the Intervention

Step 2: Create a Logic Model

A logic model is often used in an evaluation to visually depict the "theory of change" behind how an intervention is intended to influence outcomes. Generally, a logic model is read by column from left to right and it includes directional arrows and lines to illustrate causal relationships between the intervention inputs, activities, and outputs and the short, intermediate, and long-term outcomes. Although the logic model is frequently a linear concept map, it can be complex in terms of the number of relationships among inputs, activities, and outputs and the resulting outcomes as well as the potential feedback and influence of the outcomes on the inputs, activities, and outputs.

Logic models should reflect process evaluation, impact evaluation, and outcome evaluation elements. The process component of the model will describe what is needed in the planning phase of the intervention, while the outcome elements in a logic model demonstrate the intended effect or goal with respect to a given time period. The table below provide descriptions of key logic model components.

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Two other important components that can be added to a logic model are "assumptions" and "external environment." The goal of a logic model is to communicate relationships between the intervention’s inputs, activities, outputs, and outcomes, and to convey the assumptions and external factors that may influence these relationships.

The word “logic” in logic model also explicitly illustrates the importance of logical connections between components within the model. The table below lists examples of pedestrian safety intervention activities and short-term and long-term outcomes that could potentially be logically linked to these activities.

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Examples of three different logic models that you can use to inform the design of your own intervention’s logic model are here:

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There are other models that can be useful to map out the relationship of the intervention. For example, the Social Economic Model (SEM) or the Action Model are frameworks that provide a visual representation of the network of interactions between an individual, their interpersonal relationships, organizations, community, and policy.

Logic models are designed to illustrate the intervention in a clear and concise format. Keeping it simple will keep you, your team, and the intervention on track.

Next: Continue to Section 3
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