a variation of the pretest–posttest design in which only a single set of participants is measured on a dependent variable of interest, exposed to a treatment or intervention, and then measured again to determine the change or difference between the initial (pre-) and second (post-) measurement. The lack of a control group in this type of research design makes it difficult to attribute gains in the posttest score to the intervention, as other elements (e.g., participant maturation) may have contributed to any change observed. Also called one-group pre–post design.