2.10. Statistical Analysis
REGRESSION
Assuming an annual admission rate of 500 patients during 1 year of the study enrollment, we planned to achieve a sample size of at least 100 patients. Sample size was calculated for the difference in postoperative cytokine levels. A total of 100 patients were needed for a significance level of 0.05 and a power of 90%. Each study group consisted of 50 patients for a total of 100 patients. To analyze our quantitative variables, we used the Kolmogorov–Smirnov test to determine their distribution. After conducting the test, we found that only age was distributed normally. As a result, we used the The quantitative variables are presented by mean and standard deviation and/or median and interquartile range (IQR). The qualitative variables are presented by their distribution by percentage. For multivariate analysis, quantile regression was applied because dependent variables are not normally distributed. We performed quantile regression for the following quantiles: 0.1, 0.25, 0.5, 0.75, and 0.9. 