2.7. Statistical Analysis

The results (RQ value) are shown as medians. Statistical analysis was performed using Statistica 13.1 software (StatSoft, Cracow, Poland). The Mann–Whitney U test was used to assess the statistical dependence between the study groups. Spearman’s rank correlation coefficient was used to measure the direction and strength of the relationship for individual variables. The level of correlation was fixed in the following categories: very strong (rho ≥ 0.80), moderate (rho = 0.60–0.79), fair (rho = 0.30–0.59) and poor (rho ≤ 0.29). Statistical significance was assumed for p-values < 0.05.