In my opinion your a welder, when you can be confident, (not hopeful), your welding job will not fail. Experience is they only avenue to this level.
I have worked with people who were paid to weld, whom were not welders. (see above).
Even being certified, does not guarantee a welder. Junior welders can sometimes pass the test, but, fail in the field. It is not that unusual to see people sent home from field welding jobs, who passed the test.