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
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%