Review Question - QID 7760

A factorial randomized control trial design is more easily represented in a two by two table. Practically, patients are randomized to either treatment A and B, treatment A or control, treatment B or control, or no treatment. The strength of this trial design is that two interventions can be assessed with the same study population. Also, any interaction between the treatments can be determined (for example, does treatment A work differentially when combined with treatment B). The parallel design trial is the simplest and most classic design for a randomized controlled trial. In this trial design, participants are randomized to two or more groups of different treatments and each group is exposed to a different intervention and only that intervention. In the crossover design trial, both groups receive both interventions over a randomly allocated time period. Group A can receive the treatment, and after a suitable washout period, can receive the placebo. Group B can receive the placebo and later can receive the treatment; this produces within-participant comparisons. The crossover trial design has a limited role in surgical interventions because it is difficult or impossible for patients to receive both treatment interventions, such as plate and nail fixation, or a cemented versus a cementless total hip arthroplasty. Case control and case series are not randomized trials, but observational studies.