Is there any difference between research hypothesis and research questions: if there is any difference where do we use them?

Research question is in a question format whereas research hypothesis is a propositional statement albeit both contain constructs / variables & their relationships that need to be empirically tested.  Research hypotheses predominantly used in quantitative research.

Agreed - I came across some researchers / scholars only include research question(s) & excluded research hypotheses in their quantitative research articles (this might create / cause concern to some readers that try to search for hypothesis in the entire article).  However, most of the articles that I'd gone through still include hypotheses.  Personally I prefer hypotheses to be included especially hi-lighted in italics which make them easily to be spotted.

The research question is more general than the research hypothesis. In a qualitative approach your don't do hypothesis testing. Statistical inference refers to a hyothesis and a null hyothesis (the one you have to adopt when you cannot verity the hypothesis). In qualitive researh or in grounded theory you can also have presuppositions, though you try to keep them low in order to give your dialogue with data a afir chance. Hypotheses in qualitative research have to do with your theoretical sensitivity, with your "Vorverständnis", due to the hermeneutic background the meaning is different from working with hypotheses in a quantitative approach.

Is there any difference between research hypothesis and research questions: if there is any difference where do we use them?

Research question is in a question format whereas research hypothesis is a propositional statement albeit both contain constructs / variables & their relationships that need to be empirically tested.  Research hypotheses predominantly used in quantitative research.

Agreed - I came across some researchers / scholars only include research question(s) & excluded research hypotheses in their quantitative research articles (this might create / cause concern to some readers that try to search for hypothesis in the entire article).  However, most of the articles that I'd gone through still include hypotheses.  Personally I prefer hypotheses to be included especially hi-lighted in italics which make them easily to be spotted.

Your question is really good but it needs bit more clarity as: there can be difference between hypotheses and propositions as hypothesis is used in quantitative research while propositions are used in qualitative research. About research questions, we can use in both types of research and it depends on what specific point we want to explore. To test one hypothesis, there may be more than one research questions in order to explore the nature of reality and then test it. 

The following papers may also help: 

• Farrugia, P., Petrisor, B. A., Farrokhyar, F. and Bhandari, M. (2010). Research questions, hypotheses and objectives. Canadian Journal of Surgery, 53, 4, pp. 278-281.
• Thabane, L., Thomas, T., Ye, C. and Paul, J. (2009). Posing the research question: not so simple. Canadian Journal of Anesthesia, 56, 1, pp. 71-79.

Research is only a means to an end and there are no fixed principles with regards having a hypothesis and research questions together. In my view it is all upto a researcher, how to construct his or her research plan to reach an answer. Please do not be a slave to a particular methodology. Experiment, mix and match and don;t be afraid of conventions. 

It depends on your location in the study an the kind of constructs that you are working with and how comfortable you are with your research design. The hypothesis in my perspective is more attuned to scientific and empirical research design whereas research questions fit more in with mixed methods and qualitative studies, as pointed out by Tughral Yamin

In exploratory research you try to assess items that are not covered before, so you may go for research questions. When you move towards descriptive research you may use either questions and hypotheses, and in causal research you also go for both with more quantitative tools. All through this process you need to be sure about what your objectives are in doing the research.

In my personal opinion, research questions are asked in qualitative research and primarily in introduction part itself. At the same time, hypothesis is used for quantitative research after valid arguments in literature review. Sometimes, they both used simultaneously in same research. 

Kindly do through these articles linked.. They may give you a bit of clarity...

 Yes, of course,  there is a difference;   you can have a research question and hypothesis. Research questions should be answerable and your hypothesis should be testable as a complementary to your research question's answer, you can have them both or either one. But, should bear in mind, that,  hypothesis directly derive from your research questions where as proposition derive from a theoretical standpoint. A hypothesis is a quantitative terminology while proposition is as qualitative, and should not use them interchangeably..

In experimental and quasi- expermental  studies, research need to use hypostheses.

however, in descreptive or survey studies, mostly questions will be enough

Research questions are questions derived from the hypothesis, they are more general. However, hypothesis is basically  statement by the researcher that speculate an outcome. The hypothesis is tested empirically with statistical tools.Largely used in quantitative research.

RQ is the issue which you want to address through your research. To address the RQ, you derive hypothesis. It may be one or more for a RQ depending upon the RQ. The hypothesis is an statistical statement, which can be tested through statistical method. However, it is not always true that all RQ must have Hypothesis.

Such as one wish to know about the economic status of a community or region or nation. This sort of RQ does not contain hypothesis. So hypothesis is basically testable.

Regards

rajiv

Research question is a question, a research study sets to answer. it can be used if there is a little previous research and is used in both quantitative and qualitative studies further, it allows a wide range of outcome.

Hypothesis is a tentative prediction. it can be used if there is significant knowledge or previous research on the subject. Hypothesis are mainly used in experimental quantitative studies and it doesn't allow wide range of outcome.

Research question is simply a question that needs to be answered through a scientific inquiry using research method something like that BUT  hypotheses is a guess that needs to be addressed to prove that whether it lies in prediction/guess or not...!