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Thumbnail of data collection design model. Click to open. Click to open the data collection design model.

A pre- and posttest design measures outcomes among program participants before and after the intervention. The image at right illustrates what pre- and posttest-only data collection looks like in a preexperimental study.

This design is relatively easy to implement. You simply administer the same measure twice, before and after the intervention. The timing of the posttest measure is important. It should allow enough time for your program to have an effect, but not so much time that program effects are diluted or influenced by confounding factors such as participation in other programs or participant social, psychological, or environmental circumstances. (Controlling for confounding factors is an important part of research quality that we discuss later in this course.)

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