2.5. Statistical analysis
The data was processed using Statistica TIBCO Software Inc. (2017)
version 13.3 soft-ware, which was licensed by the Medical University of
Silesia in Katowice. To assess the normality of distributions, we used
the Shapiro-Wilk test. Values are presented as means and 95% confidence
intervals or medians with Q1–Q3 values. To compare quantitative
variables the t-test for independent means and t-test for dependent
means were used. To compare independent variables with an abnormal
distribution U Mann- Whitney test was used. For dependent variables we
used Wilcoxon test. We assumed a p-value of less than 0.05 was
statistically significant. We also use Spearman rank correlation to
assess the relationship between variables. We assumed a p-value of less
than 0.05 was statistically significant.