Data entry and statistical analysis were done on the
Epiinfo Software, release 6, distributed by the Centers
for Disease Control, Atlanta, Georgia, USA. Two-tailed
statistical tests were used, with an admitted a error of
5%: w2 test for dichotomous or multinomial qualitative
variables, Kruskal–Wallis test for quantitative variables
with nonhomogeneous variances or nonnormal distribution,
and ANOVA for quantitative variables of
normal distribution and homogeneous variances. A
Spearman rank correlation was applied for association
between ordinal variables.