Final commentary

In order to answer a complex research question, one would have to define the research question to begin with (if not already defined). This can be very important, Haibo’s theory [1] was that you should put 90% effort into the definition of a problem and 10% on the solving the problem.
A research question definition explanation was included in the last seminar, where the book “Building Theories from Case Study Research” included the definition in the very first step. As I understood it, the reason for the definition is to focus the efforts in the research so you for example can reduce the amount of data gathering [2].

I think while there are several methods to answer research questions, perhaps they are divided into categories and sub-categories or divided into their own category. For example, one could put qualitative methods and quantitative methods in the same category and case studies in its own.

So to categorize methods in one way:

General research methods
Qualitative methods
I think the best strengths of the qualitative method is the depth and the unexpected results it can achieve. The time consumption may be its disadvantage.

Quantitative methods
I think the quantitative method especially have its strength when one have already narrowed the research down and need specific reliable data.

Combination of qualitative method and quantitative method
I think the methods can complement each other very good when both used in a research. Of course, one would need to know when to use them, for example the paper “Educational magic toys developed with augmented reality technology for early childhood education” [4] (which I chose in Theme 6 for the qualitative research questions) I think have good use of both the qualitative and quantitative method. For example, the qualitative method was used to gather the children’s opinions for example while teacher’s opinions were gathered through a survey (quantitative).

Case studies
Case studies can combine both qualitative and qualitative methods but perhaps qualitative method gives most strength to the case study research. I believe so because the observation of the ongoing case study can give much value as many unexpected events can happen, but qualitative method is more of a direct method where you already have asked the questions and limited the number of answers.

Design research
On the UX website uxbooth.com [3] the design research is explained in relation the user-centred design process. This is a practical design research process I think, with an end-user in mind. You have a proposed idea, you do initial design thinking, you make a prototype and test the prototype for the audience and receive feedback while having techniques to analyze the process. In the research paper ‘Demystifying “Design Research”’, they mention that design research by academics is different as I understand it. It can be a ‘kind’ of research, basically a “practice-based” research, comparing to for example research in mathematics or physics. It can be a part of a larger design practice which I think can mean that its result might not be directly implemented as a solution but can be a part of the whole design solution in the end [6].
In design research I think you can probably combine both qualitative and qualitative methods. Case study can be used in design research. It can be used to validate and analyze the research but it can also be used to conduct the design research according to the paper “Case study method for design research”. It is said in the conclusions that case study are of good use when developing theories in design research [8].

The philosophic approach
The philosophical approach I think can include reasoning one way from the definition of the problem to the answer or solution to the problem. You look beyond the empirical research and facts, not necessarily relying on the direct observation, like A priori. Although I should need a source here, the term A priori have I seen been used in one research paper at least.
In the metaphysics you basically can go beyond the empirical research, which makes it useful.

Discussion
I think it can be quite difficult to combine some of these methods to answer a certain research question. I guess it really depends on what kind of research one is conducting.
Some thinking around different topics is as follows.
In order to answer humanistic questions, I think one could use the philosophical approach, while considering on using other methods. Historically, I think empirical observations have changed the world view quite a bit, so empirical research could be a chosen method as well.
To come up with solutions to sustainability problems one might use design (research) thinking to come up with solutions, perhaps rather than philosophical thinking. Quantitative method can be used to analyse the current state of the sustainability field.
In order to discover potentials in new and innovative technology, one could use design research with prototyping and test the prototype with an audience together with a qualitative or quantitative analysis. Here, I think the philosophical thinking more likely would be ruled out.

Combining methods can reduce bias in one’s research, although this is something I saw being mentioned on a UX (User Experience) website [5] you could apply this for other research as well. One method is called Triangulation which means that you use more than one method in order to strengthen the research. The internet article “How Triangulation Strengthens Action Research” describes the method as to research A and research B results in C where C could never be achieved without both A and B [7]. If one research let’s say a survey have biased results because of a external factor, the other research which takes a different approach but still on the same subject could bring balance back to the research.
Combining methods can be quite effective, I think it also can be important to use the method which is most suitable for the research. Knowing when to use the qualitative and the quantitative method, depending on the time and costs of the research, number of possible participants etc.

References
[1]
Li, H. (2015). Theme 5 - Haibo Li's slides (Lecture).[2]
Eisenhardt, K. M. (1989). Building Theories from Case Study Research. Academy of Management Review, 14(4), 532-550.
[3]
Maier, A. (2010). Complete Beginner’s Guide to Design Research. URL: http://www.uxbooth.com/articles/complete-beginners-guide-to-design-research/ Retrieved Oct 2015.[4]
Rabia M. Yilmaz, Educational magic toys developed with augmented reality technology for early childhood education, Computers in Human Behavior, Volume 54, January 2016, Pages 240-248, ISSN 0747-5632, http://dx.doi.org/10.1016/j.chb.2015.07.040.
[5]
Kennedy P. (2009). How to combine multiple research methods: Practical Triangulation.
URL: http://johnnyholland.org/2009/08/practical-triangulation/ Retrieved Oct 2015.
[6]
Faste, T, Faste, H. (2012). Demystifying "Design Research": Design is Not Research, Research is Design, IDSA Education Symposium. URL: http://www.idsa.org/sites/default/files/Faste.pdf
[7]
Murphy, J. (2011). How Triangulation Strengthens Action Research. Bright Hub. URL: http://www.brighthub.com/education/postgraduate/articles/112609.aspx Retrieved Oct 2015.
[8]
Teegavarapu S, D. Summers J. (2008). Case study method for design research. The American Society of Mechanical Engineers.
URL: http://www.clemson.edu/ces/cedar/images/0/07/Case-study-design-research.pdf