<qa>  What is the standard deviation of mean?Statical Analysis Statistical analysis was applied using SPSS 19.0 statistical software.our sample size calculation method is dixon and massey up and down method. According to this account, n 2 SD SEM 2; n: sample size, SD standard deviation: The standard deviation, SEM standard error of mean is calculated as the standard error of the mean SD 5 mL, SEM 1.0 mL n were found in 50 patients. For the aplicational errors we add 5 patient 10 . A total of 55 patients were included in the study. 