ABA Exam CoachLessons · D. Experimental Design
D.3 · Threats to internal validity
Your data show a big change once treatment starts. So did your intervention cause it, or was it something else? Let's learn to spot the usual suspects.
Key takeaway
Internal validity is how confident you can be that the independent variable, and not something else, changed the behavior. A threat is any uncontrolled variable that could also explain the change. A discrete outside event points to history, slow change inside the person over time points to maturation, a change in how you measure points to instrumentation, and repeated measurement changing the behavior points to testing. Single-case designs control these threats with stable baselines, replication, IOA, and treatment integrity checks.
Internal validity is how confident you can be that the independent variable, and not something else, changed the behavior. A threat is any uncontrolled variable that could also explain the change. A discrete outside event points to history, slow change inside the person over time points to maturation, a change in how you measure points to instrumentation, and repeated measurement changing the behavior points to testing. Single-case designs control these threats with stable baselines, replication, IOA, and treatment integrity checks.
Members get the full lesson video, notes and a 5-question test
The video walks through the idea, worked examples, the trap people fall into and an exam-style question. The notes and the checkpoint come with it, and your results feed your Where to focus plan.