Appropriate Controls

A control treatment is a baseline treatment against which one or more other treatments will be compared. Depending on your question, this can be an untreated treatment, a procedural treatment, or a different treatment to that of the treatment group. Determining the appropriate control can be difficult. In an experiment done by researchers to examine how foxes and wolves affect plant communities, they set up fenced plots to exclude predators and outsiders. The hypothesis was the excluding predators in fenced plots will cause higher rodent populations, leading to greater seed predation and dispersal since rodents consume them. But, the result of this was that fenced plots had lower rodent populations because hawks would perch themselves on the fence posts and prey on the rodents. The fence posts unintentionally caused a higher predation rate inside the predator-excluded plots. A better control for this treatment would be to put posts all round the area that is being examined so that they mimic the real fence posts and all hawks don't perch solely on the posts put in for the fences.