Measurement-to-Design-to-Intervention Chain
Key Takeaways
- Measurement decisions determine how much confidence the BCBA can place in visual analysis and treatment decisions.
- Single-case design logic depends on repeated measurement, prediction, verification, and replication.
- Intervention changes should follow data patterns, procedural integrity checks, and assessment results.
- A mixed-domain item often tests whether the learner keeps the decision chain in the correct order.
The Decision Chain
Think of case analysis as a chain. A weak definition damages measurement. Weak measurement damages graph interpretation. Weak design damages causal claims. Weak causal claims make intervention decisions less defensible.
Domain C asks whether the data represent the behavior. Domain D asks whether the design can demonstrate a functional relation. Domains G and H ask whether procedures and implementation decisions follow assessment, evidence, client preference, contextual fit, and ongoing data.
Chain Check
| Link | Exam check |
|---|---|
| Definition | Can observers identify the response and nonexamples? |
| Dimension | Does count, rate, duration, latency, IRT, or trials to criterion match the question? |
| Method | Is measurement direct, valid, reliable, and feasible? |
| Baseline | Is there enough stable or interpretable data for prediction? |
| Design | Is reversal, multiple baseline, multielement, or changing criterion defensible? |
| Procedure | Does it match function, skill deficit, risks, and setting? |
| Integrity | Are staff implementing as planned? |
| Decision | Do data support continuing, modifying, or ending the plan? |
Design-to-Intervention Examples
Use a reversal design when withdrawal is ethical and behavior is reversible. Use multiple baseline when withdrawal is unsafe or impractical across behaviors, settings, or participants. Use multielement when rapidly comparing conditions or procedures. Use changing criterion when gradual stepwise change is expected.
Do not select a design only because it is familiar. Select it because it answers the case question while managing ethical and practical limits.
Modification Rule
Before changing an intervention for weak effects, check definition drift, data quality, procedural integrity, dosage, competing contingencies, motivating operations, and whether the functional hypothesis remains plausible.
A BCBA wants to know whether a new transition routine reduces elopement. Staff record only whether elopement occurred at least once per day, but episodes vary from 1 to 15 times daily. What is the most important concern?
A severe self-injury plan appears effective after intervention begins with one client. Withdrawing the plan would be unsafe. Which design is most likely defensible if replication can occur across settings?
A graph shows no improvement after a function-based intervention. Integrity data show staff implemented only 35% of planned antecedent strategies. What should the BCBA do first?