Does peer victimization during adolescence have an impact on depression in early adulthood? A recent study in the United Kingdom examined data on 3898 participants for which they had information on both victimization by peers at age 13 and the presence of depression at age 18. The study found more than a twofold increase in the odds of depression between children who were not victimized and those who were frequently victimized.20 This is an example of an observational study. a randomized comparative experiment. a matched pairs experiment.

A randomized comparative experiment is to perform a comparative experiment in which some individuals receive one treatment and similar units receive another. The solution to the problem of bias is a random experiment, where individuals are assigned to treatments using some type of chance process.

Comparison alone isn’t enough if the treatments are given to groups that have great differences, as bias will result, they can be a solution to confounding though, controlling the effects of lurking variables on the response, replicating in enough subjects in each group to reduce chance variation in the results.