If I were doing an evaluation of an existing after-school program where involvement was voluntary, would I do a quasi-experimental design or experimental design?

I'm thinking quasi-experimental as I would randomly select from those who are enrolled in the program.

I'm not sure what you mean by "quasi-experimental."

What criteria are you using to evaluate the program? Are you having a control group?

To determine whether to use a quasi-experimental design or an experimental design for evaluating an existing after-school program with voluntary involvement, consider the following:

1. Quasi-experimental design: This design is suitable when you cannot randomly assign participants to different groups. In your case, since involvement in the after-school program is voluntary, you cannot randomly assign students to participate or not. Instead, you can compare the outcomes or measures of those who volunteered for the program with another group who did not participate. This design is likely to be more feasible for your evaluation.

Here's how you could proceed with a quasi-experimental design:
1. Identify a control group: Select a similar group of students who are not participating in the after-school program. Ideally, they should match the program participants in terms of characteristics like age, demographics, or academic ability.
2. Collect baseline data: Before starting the evaluation, gather data on the outcomes you want to measure (e.g., academic performance, behavior, social skills) for both the program participants and the control group.
3. Implement the after-school program: Allow the students in the program group to participate in the after-school program.
4. Collect post-program data: After a suitable period, collect the same outcome measures again for both groups.
5. Analyze and compare results: Compare the post-program data between the program participants and the control group to assess any differences in outcomes.

An experimental design, on the other hand, involves randomly assigning participants to different groups, such as a treatment group (students who participate in the after-school program) and a control group (students who do not participate). Since you cannot randomly assign participants in your case, a quasi-experimental design is a more appropriate choice.

Remember, the choice between experimental and quasi-experimental designs depends on the available options and the practical constraints you face when evaluating a voluntary after-school program.