Block randomization using the site www.randomization.com. For equal gender distribution, 25 people, including women, are randomly divided into two groups (12 and 13 people) by the randomization site, and to see which group to use what type of toothbrush, We choose between the two groups in a simple random way. Now the numbers obtained from the site For example, numbers 1،6،7،10،11،12،13،14،15،17،21،22،23 (The numbers indicate the order of arrival of the clients). For a group And the numbers 2,3,4,5,5,8,9,16,18,19,20,24,25, we consider for the other group.
now we do the same for the male group.