1. First, prepare the corresponding number plate or note, and write the number of each subject on it.
2. Put the number plate or note into an opaque container or bag.
3. The experimenter needs to randomly extract a corresponding number of numbered cards or strips from the container or bag without looking at them, and the probability that the number of each experimental object is extracted is the same.
4. According to the needs of the experiment, the extracted numbers are divided into different groups, and the corresponding processing and experiments are carried out.