Applications of a sequential alternating treatment design.

Barnes et al. (1990) drew a new single-case blueprint. They call it the sequential alternating treatments design. You start two treatments right away. No wait for a long no-treatment line. You stagger the start times across two behaviors, people, or settings. Control comes from the stagger, not from a quiet baseline.

The paper shows the plan with made-up graphs. No real kids or clients took part. It is a map, not a trip report.

There are no numbers to report. The authors simply show that the stagger lets you compare treatments while skipping the usual baseline phase. Ethical problems melt away when you must act fast.

Rojahn et al. (1987) ran the first warning test. They found that alternating treatments within one day can blur the picture unless you leave two hours between them. Barnes et al. (1990) borrow that spacing idea and add the stagger trick. The two papers fit like Lego blocks.

Lloveras et al. (2025) push the idea further. They tell you to stagger across two axes at once, such as kid plus setting. Their compound multiple-baseline design is the grandchild of D et al.'s 1990 plan. Both aim to keep control when baselines misbehave.

Joo et al. (2018) look at the other end. They ask, What if you keep the baseline but let data guide how long it runs? Their sims say extra baseline days do not hurt your stats. Barnes et al. (1990) answer a different question: Skip the baseline entirely. The two views seem opposite, yet they serve the same goal—clean control with less waste.

You can now start two good interventions tomorrow instead of waiting a week for baseline data. Use the sequential plan when a no-treatment stretch is unsafe or simply rude. Just remember to space sessions at least two hours apart, as Rojahn et al. (1987) proved, and stagger the starts across kids or tasks. You keep experimental control and your client gets help right away.