Qualitative By Dave Collingridge I remember years ago walking the halls of the faculty offices at my university asking for help on validating a questionnaire.
I repeatedly asked professors, “Can you tell me how to validate the questions in my survey?
Development of a valid and reliable questionnaire is a must to reduce measurement error.
Groves (1987) defines measurement error as the "discrepancy between respondents' attributes and their survey responses" (p. Development of a valid and reliable questionnaire involves several steps taking considerable time.
One of the most used questionnaires worldwide to analyse these problems is the Internet Addiction Test (IAT).
It could be anything from the way the question is worded and how it was understood by respondents to the violation of assumptions such as normal distribution of data etc.
It’s a little bit of extra work but is great for showing how well you have though about the robustness of your conclusions.
Comparison with Other Questionnaires You may wish to add an existing questionnaire in addition to your items and comparing how they measure differences on that construct e.g.
GAD-7 versus your own anxiety and depression questions.