This chapter discusses analysis and interpretation of collected data as three steps: Preparation of data, data analysis, and interpretation of results. In quantitative data studies preparation requires cleaning data, followed by statistical analyses of demographic and study variables. Those results are then interpreted to answer each hypothesis or research question in the context of statistical validity (i.e., Type I and Type II errors), clinical meaningfulness, and internal and external validity. In contrast qualitative data preparation involves organizing data, followed by integrated data analysis and interpretation. Finally, methodological, mixed methods, ideological, and historical researchers adapt relevant quantitative and/or qualitative analyses and interpretation of data using their own unique models and methods.