Subjects can be randomly assigned to the experimental group and the control group by flipping a coin (both sides are designated as the experimental group and the control group respectively), drawing lots, using a random number table or adopting a systematic randomization method, that is, using ready-made data (such as subject serial number, ID number, medical record card number, work number, student number, etc.). ) alternate.
After random grouping, when the sample size is large, each group is not completely equal, so experimental research can generally be carried out. When the sample size is small, the number of individuals in each group is quite different, and it needs to be randomly regrouped until the predetermined balance requirement is reached.