The next step is to create your evaluation design(s) with respect to one or more of your evaluation questions and the associated types of evaluation. As noted in the previous step, you want to maximize your ability to say that the pedestrian safety intervention caused the changes in outcomes observed. Although many pedestrian safety evaluations will not be able to show full causality, or attribution, your evaluation can show that the combination of intervention activities contributed to the observed outcome of interest. Causal inferences increase confidence in the internal validity of the relationship of the intervention to the outcomes observed. Rigorous evaluation designs help to minimize threats to internal validity.
Tools and Resources
Evaluation Design Illustrations4
This table shows descriptions, examples, and graphic depictions of each evaluation design along with causality and strength of attribution.
Although you’ve learned about the many types of evaluation designs you and your evaluation partners can use, you’re probably wondering how to determine the evaluation design you should use.
The short answer: Choose the design that can best provide the data you need to:
However, there are likely several designs that could provide these data, and you want to choose the design that will maximize your causal inference.
Therefore, your next step is to consider the strengths and weaknesses of each evaluation design in minimizing threats to internal validity. Your final decision will need to strike a balance between getting the best possible data and making the most efficient use of available resources within your timeline.
There are three basic conditions necessary to establish causality, including:
With these conditions in mind, there are seven basic threats to internal validity and their relationship to evaluation designs:View the Resource Table
Tools and Resources
Evaluation Design: Strengths and Weaknesses5,6,7,8,9,10
This table shows strengths and weaknesses of each design, along with a description and example pedestrian safety intervention evaluations for each design.