1 Department of Educational Psychology and Counseling, National Taiwan Normal University, 162, Section 1, Heping E. Road, 10610 , Taipei, Taiwan. cwliu@ntnu.edu.tw.
2 Centre for Educational Measurement, University of Oslo, Oslo, Norway.
3 Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway.
4 Graduate School of Education, University of California, Berkeley, Berkeley, CA, USA.