Application of SPSS linear mixed methods to adolescent development research: Basic concepts and steps

In the context of intervention research, it is always important to ask whether the growth of the participants in the intervention group is superior to that of the control group participants. Although this question can be answered by analyses based on traditional generalized linear models (GLM), there are many problems associated with such analyses. Alternatively, individual growth curve modeling (IGC) analyses based on linear mixed methods (LMM) are proposed. Although linear mixed methods are available in generic computer software such as SPSS, there is a paucity of user-friendly manuals and illustrations. To help researchers to use SPSS to conduct individual growth curve models, the basic concepts of individual growth curve modeling and the steps of using SPSS to conduct IGC are presented in this paper.