Table 3.

The selected demographic characteristics and the initial values of medical absenteeism of the intervention and control groups

	Intervention group (493)	Control group (445)	Statistical values
Gender, % female	55.8*	64.3	χ 2 = 7.01**, df = 1
Age in years, mean (SD)	14.54 (1.32)	14.32 (1.28)	t = 2.49*
Absence rate in periods per 12 school weeks, mean (SD)	3.91 (1.62)**	4.50 (1.16)	t = −6.20**
Absence rate in days per 12 school weeks, mean (SD)	8.40 (5.39)*	9.92 (5.39)	t = −4.27**
Number of days per period	2.29 (1.53)	2.39 (1.67)	t = −0.95

* p ≤ 0.05; ** p ≤ 0.01