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Table 2 Relative frequencies of Stomach ache among grade 5, 7 and 9 students, distributed by gender and menarche

From: Explaining differential item functioning focusing on the crucial role of external information – an example from the measurement of adolescent mental health

 

Boys

Girls no period

Girls period

n = 9153

n = 3676

n = 5446

Every day

2.1%

3.7%

5.5%

More than once a week

5.5%

8.0%

13.6%

Once a week

11.3%

15.5%

16.8%

About once a month

29.0%

28.7%

44.0%

Seldom or never

52.2%

44.1%

20.0%