Ammar Hameed Shnain, by using Validity, you would be trying to establish if the questionnaire is 'measuring' what is intending to measure. This depends on the questions you ask. Further, there are three general types of validity to consider: face, content, and criterion. Can you work with a member of your committee on these topics or someone from your University that can help, e.g. a statistician?

Your research sounds interesting, are you developing IoT systems?

Cory Jensen thank you a lot . Yes I will developing IoT system based on theoretical model

Thank you for your question. First, I would encourage you not to develop a new questionnaire but to search the literature for questionnaire published in the literature and get permission for using them. Creating a new questionnaire is not an easy job.

Regarding your question, reliability is about test-retest, meaning a tool should provide the same measures if re-used under the same conditions. There are several types of validity (about 20 types). However, the common types are face-validity, content validity and construct validity. Face validity is about what participants think about the questionnaire (for example, during the piloting of the survey). For instance, if they reported the questions were not clearly written, the questionnaire was too long, several statements could have several meanings; this means the questionnaire has low face validity.

I think I cannot go through all these types of validity. I recommend you read the following textbook on the questionnaire.

W F Moroney and JA Cameron. Questionnaire Design: How to Ask the Right Questions of the Right People at the Right Time to Get the Information You Need (Users' Guides to Human Factors and Ergonomics Methods) Paperback – February 15, 2019

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