A practical example of a one-group pretest-posttest design involves evaluating an anti-drug education program for elementary school students. Researchers first measure the students' baseline attitudes toward illegal drugs (the pretest). Next, they implement the anti-drug curriculum over a specified period. Finally, they measure the students' attitudes again (the posttest). By comparing the pretest and posttest scores, researchers can see if attitudes changed, though the lack of a control group makes it difficult to definitively attribute any change solely to the educational program.