We make a couple of important notes. First, for the comparison between the "seed" and "control" groups to make sense, however, both groups need to be independent from each other. Otherwise, they could influence each other’s results. This means that a participant being selected for the "seed" or "control" group has no influence on another participant being assigned to one of the two groups. As an example, if there were a mother and her child as participants in the study, they wouldn’t necessarily be in the same group. They would each be assigned randomly to one of the two groups of the explanatory variable.