If I adapted my questionnaire from a previous published paper (used the same questions with minor changes), is it enough to ensure validity? what the practical steps to ensure validity of questionnaire please? Regards
When you modify/adapt an original questionnaire, it is recommended to test the validity of this modified version to ensure the measurement properties of this new version. It is simple to be done, just collect data from a sample using the original questionnaire and the modified version you got, and then estimate the concurrent or criterion validity (correlation statistics). If they present a very good to excellent association, then the validity of this modified version is demonstrated.