*Geek Box: Parallel Design
You’ve likely heard of randomised controlled trials referred to as the “gold standard” research design, and a parallel design is the gold standard in drug trials, because the study compares two treatments: drug vs. placebo. The essence of a parallel design is that participants only receive the intervention they are assigned to. This is contrast to crossover designs, which we had in a Geek Box in this study, where the treatments are run in different order.
So, in a crossover design, participants get Diet A followed by Diet B, while the other group may get Diet B followed by Diet A. A parallel study does not necessarily have to test the intervention against a placebo; it could have parallel groups of different types of intervention, as is the case in this study, where two different diets are being compared against each other. So, in a parallel study, participants only get the intervention they are assigned to, not all interventions. Therefore, participants assigned to Diet A are compared to participants assigned to Diet B.