Formulating a research question well can be tricky. Here are a set of checks that you can use, both for your main question and for your sub-questions:
Is the question relevant (does it fit in with the goal)?
If the question is not necessary for realizing your solution, why would you spend time on it? This also means that your main question indicates the central question you ask to come to your solution. The main question is then divided into various aspects to form the sub-questions. So if a sub-question does not fall within the scope of your main question (and therefore your goal), the question is irrelevant (or you may have to reformulate your main question...).
Is the function clear (in terms of the type of professional product)?
Is it clear how the answer contributes? Does it, for example, does provide information for a better understanding of the problem or does it help with determining the design?
Is the question neutral? (not an opinion or already including a direction for the solution)
A big pitfall is that secretly a decision is hidden in the question, while you are actually still in a phase in which it is not yet clear that this decision is the right one for your situation.
Is the question feasible (time, resources)?
If your question is going to cost a lot of time or money to answer, then it is important to consider whether this is possible at all and if it might be possible: whether this is the best way to spend your resources.
Is it an open question? (not yes / no)
The goal of a research question is to bring out certain information. The choice for yes or no (which contains very little information by itself) is usually the result of a practical question that you wanted to answer with the help of this information.
Is the question clear? (one explanation, concise)
It is important that your question can only be understood one way, making it clear to yourself what you want to know, but also for your client, supervisor or teacher.
Tip: If you already have experience with the SMART formulation of goals and requirements, you will recognize a number of aspects from above (specific, acceptable, realistic).
Examples
A. Suppose your goal is to speed up the handling of orders at Bol.com. Which question better matches the goal (relevance)? Why?
B. Imagine you have devised an ICT solution to speed up the handling of orders at Bol.com. Now you want to evaluate that solution. Which question would more suitable as a research question? Why?
Firstly, the first question is a closed question. The answer is yes or no. The second question will give you more information: how large is the difference? Then you can still try to draw the conclusion for your practical question whether the new situation with your solution is better.
The second point s that the first question is very unspecific. Which aspect is better? What do you want to look at? This is much more concrete in the second question: you look at the processing time.
C. Say your grandmother is feeling lonely in the old people's home, and you want to help her using your experience with robots. What is a more appropriate question to start with?
Sources
Losse, M. (2011). Onderzoeksvaardigheden voor docenten. Boom Lemma.