Can you provide more detail? What do you mean by ``research questions'' and ``hypotheses.''  These phrases get used differently within the different disciplines on researchgate.

I agree that these terms can mean different things in different fields. In my own experience, research questions are generally rather broad, whereas hypotheses are quite explicit and thus stated in a form that can be tested directly.

I learnt that hypotheses are answers to the research questions.

If your quantitative study is explanatory you have to have them both.

Thank you so much for these insights!

I think hypothesis is more in meaning size than research questions, or after a researcher postulate a hypothesis, then many related research questions will be automatically and logically generated, I am talking in engineering investigations.

Regards, Emad

All research questions should be hypotheses. For quantitative you certainly need to start with hypotheses. For qualitative research you are still best advised to have clearly defined exploratory aims/hypotheses. Each research question requires a theoretical and methodology framework, and they bring hypotheses or alternative hypotheses into the piece of research. My workbook on empirical methods for law students (who are totally new to research methods) may be of help. You can download it by clicking on the link: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2407141

Yes you can have both in quantitative research study.