In scientific research, as a researcher if we want to have objective experiment we choose our test subject randomly. So every possible test subject have equal chance to take place in our experiment. It is a very reliable test procedure as its evidence eliminates fake or forced casualties, because the samples taken for observation are selected at random. For example we have treatment and control group, we separate them randomly. Randomization is used mainly to test hypothesis. We see randomization mostly in drug testing, for instance anti-depressive drug side effects. Another field that heavy use in clinical trials for health care systems which requires them to put all the new medicines and psychotherapy procedures to randomized trials before approving them.
Author: Murat Artiran, Ph. D., Clinical Psychologist