Sample size, power analysis, and statistical analysis
The sample size was calculated using G*Power© software version 3.1.9.2 (Institute of Experimental Psychology, Heinrich Heine University, Dusseldorf, Germany). The sample size was calculated for the Mann–Whitney U test, which was used for testing the main hypothesis of (VAS scores at rest in the first postoperative hour) in the preliminary study. Depending on the preliminary study research results with two-sided (two tails) type I error 0.05 and power of 80% (1-β = 0.8), effect size (d) factor 0.84, should involve ≥ 50 subjects.The post hoc power was calculated using G*Power© software version 3.1.9.2 (Institute of Experimental Psychology, Heinrich Heine University, Dusseldorf, Germany). The power was calculated for the Mann Whitney U test, which was used for testing the main hypothesis of the present study (VAS rest first hour). Depending on previous research results with two-sided (two tails) type I error 0.05 and effect size (d) factor 1.16, post hoc power calculated as %99.99.Data analyses were performed by using SPSS for Windows, version 22.0 (SPSS Inc., Chicago, IL, United States). Whether the distribution of continuous variables was normal or not was determined by the Kolmogorov Smirnov test. Levene test was used for the evaluation of homogeneity of variances. Unless specified otherwise, continuous data were described as mean ± SD for normal distributions, and median (Q