3. Statistics
Statistical analyses were performed using the SPSS software version 24. The variables were investigated using visual (histograms, probability plots) and analytical methods (Kolmogorov-Smirnor/Shapiro-Wilk’s test) to determine whether or not they are normally distributed. Descriptive analyses were presented using means and standart deviations for normally distributed variables, and using medians and interquartile range for the non-normally distributed variables. Student’s t-test was used to compare parameters which were normally distributed, and the correlation coefficients and their significance were calculated using the Pearson test. Mann-Whitney U test was used to compare paramaters which were non-normally distributed, and the correlation coefficients and their significance were calculated using the Spearman test. A 5% type-I error level was used to infer statistical significance.