Why bother using the notation to diagram the type of experimental design?
If you use the notation appropriately you can see youre way out of the brambles in such as examples as the 50-cent coupon design questions encountered in the Homework. Each of the designs has its strengths and weaknesses and if you can identify the design you know immediately what potential problems to look for. When we talk about strengths and weaknesses were really discussing potential sources of error. There are 10 potential sources of experimental error: • Premeasurement error: changes in the dependent variable that are solely the result of the effect of the initial measurement. This source of error would be present in those designs that • have a pretest (e.g., pretest-posttest with control group) • and dont attempt to control for this source of error (note: the Solomon Four design controls for a pretest measurement. • Interaction error: an increase (or decrease) in the effect of the independent variable because of a sensitizing effect of the premeasure. Interaction error occurs wh
