Observational and experimental designs
An evaluation design is the structure or framework you decide to use to conduct your evaluation. There are two main types of evaluation designs: observational and experimental.
An observational study is a study design in which participants are not pre-assigned to participate in the program or not (control/comparison group).
An experimental study involves an intentional assignment of participants to the experimental/intervention group and the control/comparison group. This allows the evaluator to alter the independent variable (the program or activity) and be able to control external factors that influence the outcome variable. Experimental designs are not always easy to implement, but are the best option for reducing internal threats to validity (for definition see section “internal validity” below).
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