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.