General design classifications.

This column described the general design classifications of between-groups, within-subjects, and mixed designs. Remember that in between-groups designs, each participant is in only one group or condition. In within-subjects or repeated-measures designs, on the other hand, each participant receives all the conditions or levels of the independent variable. In mixed designs, there is at least one between-groups independent variable and at least one within-subjects independent variable. In classifying the design, do not consider the dependent variable(s). The classifications and descriptions presented in this column are for difference questions, using the randomized experimental, quasi-experimental, and comparative approaches to research. Appropriate classification and description of the design are crucial for choosing the appropriate inferential statistic, which is the topic of the next column and several to follow.