2.4 Statistical analysis
Using previous literature as a basis, a significant difference of ≥ 0.1 mm was estimated in the carotid intima-media thickness.17,20,21 With 80% power and 95% confidence, a sample size of 18 patients per group was determined, in a sample calculated for three groups. Categorical variables are reported as percentages and frequencies; continuous variables as means and standard deviations, or median and range, according to normality. Normality was determined using the Kolmogorov-Smirnov test. Categorical variables were compared using Pearson’s χ2 test for 2x2 tables. An unpaired Student’s t -test was used to compare continuous variables. When more than 2 groups were compared, ANOVA or the Kruskal-Wallis test were performed according to normality. All agreement analysis was made with the intraclass correlation coefficient (ICC), with 95% confidence intervals (95% CI). Agreement levels were classified as poor (<0.20), fair (0.21-0.40), moderate (0.41-0.60), good (0.61-0.80), and excellent (˃0.81). For correlation, a linear regression was used. A P-value ≤ 0.05 was considered statistically significant. IBM SPSS version 22 (IBM, Armonk, NY, 2013) was used.
Results