Which countries are included in the international norm?

For OPTO, the International norm is based on the national norms (in all N = 16589):

  • UK (N=536)
  • US (N=951)
  • Norway (N=5893)
  • Denmark (N=1696)
  • Sweden (N=3863)
  • Finland (N=1192)
  • Germany (N=487)
  • Switzerland (German speaking) (N=1055)
  • Mexico (N=530)
  • France/Switzerland (French speaking) (N=386)

The International norm is a weighted average of all the local samples, ensuring equal representativeness for all countries included. National samples are included in the International norm if they have at least 300 responses locally.