Groups did not differ significantly in age, handedness, the number of times they were deployed, the time since their last deployment, and educational level as measured with the international standard classification of education (ISCED ).
This is a level 3 on the international standard classification of education scale (ISCED).
Applying the criterion based on the estimation of Eq. (1) results in the classification of education programmes into narrow and broad ones, as indicated by the check marks in Table 2 (for the underlying estimates, see Table 4 in "Appendix 1").
Our main independent variable was the number of years of formal education received by the mother, categorised according to the UNESCO international standard classification of education [ 20].
GRP: Good recruitment practices; ISCED: International standard classification of education; GCP/ICH: Good clinical practice/ international conference of harmonization; EMEA: European medicines agency.
Table 1 shows the cross-classification of education level by death certificate and the adult household member's report at baseline visit in the NHANES of South Korea.
a T-test; b Chi-square test; ISCED: international standard classification of education; SD: standard deviation; * p < .05; ** p < .01; *** p < .001.001
Of all the eligible women (n = 5,866) 49% had an intermediate level of education and 32% had a high level of education according to the classification of education of Statistics Netherlands (Table 2) [ 20].
Country-specific classification of education in the Netherlands ('low' means only compulsory education) compared to the International Standard Classification of Education ISCEDD) in Germany; ISCED levels 1 + 2 are referred to as 'low education', levels 3 to 6 are referred to as 'high education'.
A categorical education variable was generated for the mother and the father separately by applying a revised version of the 'Comparative Analysis of Social Mobility in Industrial Nations CASMININ) classification of education for Germany [ 15].
