The random division of eligible people into three groups is done using a table of random numbers. Tables of random numbers are prepared by computers that arrange numbers randomly.
These tables have random numbers in both row and column directions, which usually reach 99 rows and columns, and the numbers of the rows and columns are in blocks of five digits next to each other and in a separated form to facilitate its use.
To use the table of random numbers, the researcher must first find out the exact number of people in the society and give them a code in order. In this study, 90 people (total samples) should be divided into 3 groups of 30 people. Therefore, to each of the 90 people, two-digit codes such as 01, 02, 03, ..., 11, 12, .... 89, 90 is given.
To select sample people from the table, the researcher randomly starts from a point of the table in the row or column direction. She can choose the point by closing his eyes and placing his finger or pen tip on the table. Movement in the direction of row or column does not differ and this work is related to the researcher's desire. But due to the two-digit codes, she must choose the same number of digits in the direction of the row or column.
After this, numbers control the route. Willingly or not, she will come across two types of numbers, one of which is smaller than 90 and the other is larger than 90. She should pay attention and choose only the smaller numbers. The selected number is actually the code of an individual from the community that is selected as a sample. This work should continue until a small number can be selected for the number of sample people. After completing the sample volume, the first group is determined.
To select the second group, after removing the people of the first group from the total of 90 people, this time she does the same thing considering 60 people and 30 people are selected from them. In this way, the remaining 60 people form the third group.
Blinding method: the person who collects the data, the person who performs the statistical analysis, and the patients, do not know about the study groups.
In order to comply with the conditions of blinding, the two drugs ropivacaine and the combination of ropivacaine and dexmedetomidine in two different doses of 1 and 2 mg/kg were prepared by the operating room nurse in similar syringes with the same size and labeled with three codes A, B, C before surgery. They will be placed and daily provided to an anesthetist and he will make the relevant prescription without knowing the type of intervention. In addition, the evaluator who is responsible for collecting information and the patient will not know the type of intervention in each group. The statistical analyst will not know the type of the two groups under study. In this way, the condition of being three-blind will be established.