sequence effect
in within-subjects designs, a difference in scores that emerges because of a particular arrangement of treatments—that is, the presentation of one level of the independent variable has an effect on responses to another level of that variable. A researcher can test for a sequence effect by administering the treatments in various different arrangements (e.g., the arrangement ABC vs. ACB, vs. BCA, and so forth). The sequence effect is not to be confused with the order effect.