An experimental design in which different treatment conditions (e.g. type of intervention, questionnaire administration) utilise different subjects, and so the resulting data are independent. The most common use of this type of design is where one group receives the intervention under investigation (experimental/treatment group) and the other does not (control/comparison group)

Example: one class of pupils receives an intervention with a parental focussed component, another receives the intervention without the parental component, the final group receives no intervention at all.