Fixed, Random and Mixed Statistics is confusing enough through its massive terminology. Psychology, which is largely experiment-oriented, further confuses people by adding its own flavor. A peek at the definitions of fixed, random, and mixed effects in the APA Dictionary of Psychology exemplifies this: [A mixed-effect model is] any statistical procedure or experimental design that uses one or more independent variables whose levels are specifically selected by the researcher (fixed effects; e.g., gender) and one or more additional independent variables whose levels are chosen randomly from a …