Hello.. does anyone know how to run a validation study to validate questionnaire? thanks

For health questionnaires the respondents must be examined by a physician and the results agree. You need a very large number of people, something around a thousand.

I think that developing a standardised questionnaire is a phd in itself. I use 2 standardised questionnaires: main advantage is that I can compare with previous studies. Administrating questionnaires is bloody hard, probably the hardest part of the fieldwork.