The parallel treatments design: A systematic review
Most articles that say they use parallel treatments design actually don’t—run through the Gast & Wolery checklist before you claim it.
01Research in Context
What this study did
Frampton et al. (2021) read every paper that claimed to use a “parallel treatments design.” They checked each one against the original Gast & Wolery (1988) rules. The team wanted to see how closely real studies follow the recipe.
What they found
About half the papers skipped at least one key step. Some left out the baseline. Others forgot to counterbalance the order. Only a handful met all the old rules.
How this fits with other research
Jobin (2019) and Boudreau et al. (2015) both used the close cousin “alternating treatments” and followed every rule. Their clean contrast shows the problem is not the design family—it is sloppy labels.
Saini et al. (2020) ran a similar audit on functional-analysis papers. They also found short-cut versions that still got good data. Together the two reviews say the same thing: brief can work, but call it the right name.
Fisher et al. (2003) gave us the conservative dual-criteria (CDC) visual-inspection tool. Many PTD papers that Frampton checked were already using CDC, so the fix for better graphs is already on the shelf.
Why it matters
Before you write “PTD” in your method section, open the Gast & Wolery checklist. Add baseline, randomize order, and graph with CDC. Reviewers will smile and your data will still be sound.
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02At a glance
03Original abstract
AbstractThe identification of interventions that are both effective and efficient is an ongoing need for the practice of applied behavior analysis. The parallel treatments design (PTD) has been described as powerful tool for comparing interventions in applied settings. The PTD combines elements of the multiple probe design and the adapted alternating treatments design. Execution of a PTD requires adherence to experimental tactics related to both designs, as well as adherence to specific features of the PTD outlined by the original authors (Gast & Wolery, 1988). The purpose of this systematic literature review was to evaluate (a) publication trends with the PTD, (b) applications of the PTD across behaviors and interventions, and (c) the extent to which articles that named the PTD as the design adhered to its defining features. Outcomes are discussed with respect to the utility of the PTD, limitations of the PTD, and potential refinements of the definition of the PTD.
Behavioral Interventions, 2021 · doi:10.1002/bin.1818