2.3. Statistical analysis
Descriptive statistics were presented using mean and standard deviations for continuous variables. The chi-square test (χ²) was used for categorical variables and expressed as observation counts. Statistical significance was accepted when the two-sided P value was lower than 0.05. For comparison of two non-normally distributed groups, the Mann–Whitney U test was used. All statistical analyses were performed using IBM SPSS Statistics 26.0 was used (IBM Corp., Armonk, NY, USA).