Table 3 The selected demographic characteristics and the initial values of medical absenteeism of the intervention and control groups

Gender, % female

55.8*

64.3

χ² = 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