Statistical analysis
The data is presented as the mean ± the standard deviation (SD) along
with the minimum and maximum values (range) for continuous variables, or
as percentages (%) for categorical variables. A p-value <
0.05 was considered statistically significant. Shapiro-Wilk tests were
used to determine if the quantitative data was normally distributed.
Levene’s test was performed to verify relative homogeneity of variance.
Student’s t-tests and the Mann-Whitney U tests were used for statistical
comparisons. Correlation coefficients were calculated; to detect a
simple correlation (r = 0.25) with 80% power and a 5% significance
level (two-tailed; α = 0.05; β = 0.2), the minimal sample size was set
at 123 cases. The analysis of variance (ANOVA) or non-parametric Kruskal
Wallis tests were used to compare values between different groups.
Detailed comparisons were performed using Tukey’s post hoc analyses.
Qualitative variables were compared using χ2 (chi-squared) tests of
proportions with Bonferroni corrections to account for the multiple
comparisons. Statistical analyses were performed using StatSoft
STATISTICA 13.1 software (StatSoft Inc., Tulsa, OK, USA).