“…In these models, performance at a second time point is predicted from performance on the same construct at the first time point, along with a variable representing the assigned treatment condition (Allison, 1990;Petscher & Schatschneider, 2011;Thomas & Zumbo, 2012;Zumbo, 1999). A scan of the recent issues of the Journal of Research of Educational Effectiveness demonstrates that such designs are commonly used to assess treatment effects in educational research, with regression (e.g., Murphy et al, 2020), hierarchical linear or mixed-effects models (e.g., Gandhi et al, 2020), and Structural Equation Models (e.g., Wanzek et al, 2020). Therefore in the present work, we provide an extension to the existing literature on planned missing designs to demonstrate how to measure intervention response within the longitudinal planned missing data framework.…”