Modeling Nonlinear Growth With Three Data Points

Abstract

The purpose of this article is to demonstrate ways to model nonlinear growth using three testing occasions. We demonstrate our growth models in the context of curriculum-based measurement using the fall, winter, and spring passage reading fluency benchmark assessments. We present a brief technical overview that includes the limitations of a growth model with three time points, and how nonlinear growth can be modeled and the associated limitations. We present results for a piecewise growth mixture modeling approach to model nonlinear growth for 1 to 3 classes, as well as to further explain individual differences and to capture heterogeneity of growth patterns. We discuss our interpretation of these results, as well as the implications of different methods for modeling nonlinear growth with three occasions.