Two-Way Repeated Measures Mixed ANOVA: Insights for Medical Researchers Using Simulations

Abstract

Two-way repeated measures Analysis of Variance (RMANOVA) is widely utilized in clinical and medical research to analyze longitudinal data when subjects are measured multiple times across different conditions. This statistical approach is particularly valuable when examining the effects of interventions over time or comparing treatment responses between groups. However, its application requires careful consideration of several statistical assumptions that, when violated, can compromise the validity of results. Despite its widespread use, many researchers find it difficult to apply it correctly since they are unfamiliar with its assumptions and model structure. This paper provides a comprehensive overview of two-way repeated measures mixed ANOVA, detailing its methodological foundations, essential assumptions, implementation steps, and interpretation guidelines. Using a simulated dataset, we demonstrate the complete workflow from preliminary data assessment through analysis and results interpretation. Additionally, we provide practical implementation guidelines using common statistical software SPSS.