Individuals are selected through convenience sampling and are randomly divided into two groups: control and intervention. To achieve randomization, a method of drawing sealed envelopes is used. In this method, a number of envelopes are designated by the researcher for the intervention group, and the same number of envelopes is allocated for the control group. Then, by merging the envelopes together (drawing the envelopes), one envelope is drawn and its allocation is recorded. After being drawn, that envelope is returned to the collection of other envelopes. Then the letters are merged again, and another letter is produced. This process continues until a random sequence corresponding to the sample size is reached. The concealment of random allocation is also carried out using opaque envelopes that are sealed with a random sequence. In this method, a random sequence is first generated using the mentioned method. Then, based on the sample size of the research, a number of letters are prepared with aluminum envelopes (to ensure the content of the letters is not visible), and each of the generated random sequences is recorded on one letter. The letters are then placed in the envelopes in order. In order to maintain a random sequence, the envelopes are numbered on the outside in the same order. Finally, the flaps of the envelopes are sealed and placed in a box in order. At the time of starting the registration of participants, based on the order of arrival of eligible participants for the study, one of the envelopes is opened in sequence, revealing the assigned group of that participant. The intervention and control groups are matched based on the average ratio of gender and age.