Briefly restate the purpose of your team’s program evaluation RFP.
Describe a situation for which a single-group design might be considered for an evaluation of the general program situation of your RFP (e.g., school anti-bullying program). Why might it be appropriate in this situation? Explain.
Given your example, explain the strengths and limitations of a single-group design for use in this evaluation.
Would you choose a posttest only or pretest-posttest design? Why?
How would you try to deal with threats to internal validity as part of your planning?
For example, imagine a pilot program, "Respect-First," is mandated by a school district to be implemented with all 7th-grade students in a high-need middle school. It would be considered ethically inappropriate to select a comparable control group of 7th-graders within the same school and deny them the anti-bullying intervention. Furthermore, the risk of contamination (the control group hearing about and adopting aspects of the program) is too high within a single school setting, making a true control group unreliable. In this scenario, the evaluation would focus only on the group receiving the Respect-First program.
This single-group design is appropriate because it is practical and ethical under these constraints, and the immediate goal is likely to assess the program's general feasibility and initial impact before a wider, more rigorous evaluation is planned.
Strengths and Limitations
Strengths
Feasibility and Cost: It is the least complex and least expensive design to implement, making it suitable for pilot programs, resource-constrained settings, or when a quick assessment of initial impact is needed.
Logistical Simplicity: It avoids the logistical and political challenges associated with withholding a beneficial program (like an anti-bullying intervention) from a control group.
Limitations
Weak Internal Validity: This is the most significant limitation. Because there is no comparison group, it is extremely difficult to conclude that the program, and only the program, caused any observed changes. Changes in student behavior could be due to other factors (see "Threats to Internal Validity" below).
Lack of Generalizability: Findings may not be applicable to other groups or schools due to the highly specific nature of the single cohort.
Choice of Design: Pretest-Posttest
I would choose a pretest-posttest single-group design over a posttest-only design.
Reasoning: The pretest is crucial for establishing a baseline measurement of the outcome variable (e.g., student self-reported bullying incidents, attitudes toward peers, or observed aggressive behaviors) before the anti-bullying program begins.
Without a pretest (posttest-only design), you would only know the students' status after the program. You would have no way to prove that the outcome improved or changed at all, as the final score might have been the same even if the program had never been implemented. The pretest provides a point of comparison to measure the magnitude of change within the group, making it a stronger design than posttest-only.
Dealing with Threats to Internal Validity
In a single-group pretest-posttest design, threats to internal validity (factors other than the program that could cause the outcome) are high. While they cannot be eliminated without a control group, they can be partially managed through planning:
| Threat | Explanation | Mitigation Strategy |
| History | External events (e.g., a major news story, a school fight) that occur during the program and influence student behavior. | Detailed Record Keeping: Log all significant school-wide or community events during the program period to assess their potential influence on the data. |
| Maturation | Natural changes over time (e.g., students simply maturing and becoming less aggressive as they age). | Short Program Duration: Keep the program period as short as practical to minimize the effect of natural developmental changes. |
| Testing | The act of taking the pretest itself might sensitize students to the topic, causing them to change their behavior or responses on the posttest. | Non-Reactive/Indirect Measures: Use measures that are less obviously related to the program (e.g., peer nomination for positive behavior instead of self-reported anti-bullying attitudes). |
| Instrumentation | Changes in the measurement tool (e.g., different observers, different scoring criteria) between the pretest and posttest. | Standardized Protocols: Use highly standardized and reliable measures and train all data collectors/observers to follow identical, strict protocols for both the pretest and posttest. |
| Regression to the Mean | If students were selected because they had extreme scores (e.g., highest bullying rates), their posttest scores are likely to be closer to the average regardless of the program. | Broad Sampling: Avoid only sampling those with the most extreme scores; instead, evaluate the entire 7th-grade cohort to mitigate the risk. |
Sample Answer
The purpose of your team's Program Evaluation RFP (Request for Proposal) is to solicit bids from qualified evaluators to systematically assess the effectiveness, efficiency, and impact of a specific program. This assessment aims to provide data-driven insights to inform decision-making, such as continuation, modification, or expansion of the program.
Single-Group Design in Program Evaluation
Situation and Appropriateness
A single-group design might be considered for an evaluation of a school anti-bullying program in a situation where the program is being rolled out to a single, specific, and isolated cohort of students within one school, and there is no possibility of withholding the program from a comparable group for ethical or logistical r