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Research Onion: An Explanation

  •  May 2019

  •  6-minute read

  •  Research Methods

This post introduces Saunders, Lewis, and Thornhill’s (2011) metaphor of the Research Onion, explains why it is valuable for researchers, and briefly describes each layer of the onion with straightforward examples.

As many aspiring researchers learn when they undertake a postgraduate degree, Saunders, Lewis, and Thornhill’s (2011) metaphor of the ‘Research Onion’ can be extremely helpful when designing a piece of research. This is because thinking about the research process as a multi-stage journey, which involves not only data collection and data analysis, but also philosophical and methodological choices, ensures that the process is coherent and appropriate (Sahay, 2016).

After all, students spend years completing PhD degrees and other extended research projects, meaning that a poorly-designed research process can be calamitous for their career. If a student makes the mistaken assumption that research simply involves figuring out which data are required to answer a question, and which analytical approaches should be used, then the quality of the study is likely to suffer (Saunders and Tosey, 2013). In turn, very few people will take the study’s findings seriously, which defeats the purpose of research (Leung, 2015).

For this reason, this blog post defines and explains the main features of the Research Onion in simple and easy-to-understand terms. The post also briefly discusses the reasons why you would want to use the Research Onion to guide the planning of your research project. Please note that a full list of references (in Harvard style) is given at the end of this document.

What is the Research Onion?

The Research Onion is a metaphor devised by Saunders et al. (2011). The metaphor illustrates how the so-called ‘core’ of a piece of research (i.e., data collection and data analysis) can only be coherent when it is based on an understanding of the other essential elements of a research design: namely, the research philosophy, approaches, strategies, methodological choice, and time horizon.

As Figure 1 shows, the ‘onion’ metaphor is useful because it reflects the fact that effective research processes involve a peeling away of several layers. Although it is feasible to peel the Research Onion from the inner layers to the outer layers (Sahay, 2016), the simplest approach is to start with the outer layer, and then to move inwards (Saunders et al., 2011).

Figure 1: Research Onion (Saunders et al., 2011)

Why Would I Use the Research Onion?

If you want other researchers to take your work seriously, then you need to show that the techniques and procedures you used in your study are reasonable, credible, coherent, and – perhaps most importantly – not arbitrary. Just as I mentioned in my blog post on systematic literature reviews, good researchers, especially when they are involved in areas such as healthcare, will appraise the methodological quality of a research project.

Therefore, if you make a decision about how to gather and analyse data arbitrarily, the chances are that your work will be of little to no value to others. In contrast, if you think about the essential design elements of your research project, consider how all these design elements are related, and explain and justify them, others will have reason to take your work seriously, and to regard your findings as reliable (Saunders and Tosey, 2013).

It’s worth pointing out that while the Research Onion is a widely-used and effective way to design a piece of research, alternative models exist. These won’t be discussed in this blog post, but consider taking a look at Melnikovas’ (2018) recent article for more information. For me, the Research Onion tends to win out over other models, though, given its simple and straightforward nature.

Peeling Back the Layers of the Research Onion

Research Philosophy

A research philosophy establishes the epistemological, axiological, and ontological foundations of a piece of research (Denscombe, 2008; Saunders and Tosey, 2013). In plain English, we might say that a research philosophy is the researcher’s personal view about what acceptable knowledge actually is. Naturally enough, then, a research philosophy is the outermost layer of the Research Onion.

Various research philosophies exist, including interpretivism, positivism, realism, and pragmatism (Creswell, 2014). When you’re thinking about your own research design, consider getting to know the main features of each of these philosophies. This is because the decision you make at this layer of the Research Onion will inform every later decision you make.

To learn more about the research philosophy layer of the Research Onion, take a look at our recent blog post on the topic. Our research philosophy blog post provides a simple explanation of academic definitions of the term, and it explores axiology, epistemology, and ontology in greater depth.

Research Approach

The research approach you choose will determine the broad method of reasoning you adopt throughout your research (Burney, 2008). Certain research approaches lend themselves naturally to certain research philosophies, an example being that the so-called ‘top-down’ (i.e., deductive) approach is often paired with the positivist philosophy (Wilson, 2010).

In addition to the deductive approach, the inductive approach is the other main research approach (Zalaghi and Khazaei, 2015). It’s beyond the scope of this blog post to examine each of these research approaches, but extremely valuable resources you should consult for your research include Trochim (2006), Wilson (2010), Saunders et al. (2011), and Zalaghi and Khazaei (2015).

Research Strategy

A research strategy refers to the general, overarching plan that a researcher will use to answer their research question (Saunders and Tosey, 2013). Various research strategies exist, ranging from ethnography to experiment. Perhaps the best way to understand the concept of a research strategy is to consider an example.

One example of a research strategy is the so-called ‘case study’ strategy, in which a phenomenon, individual, or entity is investigated within its real-life context (Yin, 2003). A case study strategy could be applied by, for instance, examining an event like the Watergate scandal, or by investigating paediatric pain management practices among nurses (Heale and Twycross, 2018).

Methodological Choice

The concept of methodological choice, which simply involves choosing between quantitative, qualitative, multi-method, mono-method, and other types of research design, is basic but critical (Saunders and Tosey, 2013). Before you make a decision about this layer of the Research Onion, carefully consider your available time and resources, as well as your skills.

Time Horizon

After the techniques and procedures, the time horizon is the innermost layer of the Research Onion. The fundamental choice that a researcher must make here is whether to take a ‘snapshot’ of a population at some point in time (i.e., using a cross-sectional time horizon), or to gather data from a population at multiple points in time (i.e., using a longitudinal time horizon) (Bryman, 2012).

Techniques and Procedures

Since this is the innermost layer of the Research Onion, the decisions you make about how you will gather and analyse data in your research should be based on each of the previous layers you have already peeled back (Flick, 2011).

Things to consider include how you will collect your data (e.g., questionnaires or interviews), how you will sample your target population (e.g., probability or non-probability sampling), how you will decide what sample size you need (e.g., power calculations), who your participants will be, and what method of data analysis you will adopt (e.g., thematic analysis or a statistical technique).


Burney, S. M. A. (2008) Inductive and Deductive Research Approach. Available from [Accessed 13 May 2019].

Carnwell, R. and Daly, W. (2001) Strategies for the construction of a critical review of the literature. Nurse Education in Practice. 1 (1), 57-63.

Creswell, J. W. (2014). Research Design: Qualitative, Quantitative, and Mixed Methods Approaches. 4th edn. Thousand Oaks, California: SAGE Publications.

Carnwell, R. and Daly, W. (2003) Advanced nursing practitioners in primary care settings: an exploration of the developing roles. Journal of Clinical Nursing. 12 (5).

Denscombe, M. (2008) Communities of practice: a research paradigm for the Mixed Methods approach. SAGE Journals. 2 (3), 270-283.

Denzin, N. K., and Lincoln, Y. S. (2011) The SAGE Handbook of Qualitative Research. Thousand Oaks, California: SAGE Publications.

Flick, U. (2011) Introducing research methodology: A beginner's guide to doing a research project. London: SAGE Publications.

Heale, R. and Twycross, A. (2018) What is a case study? Evidence-Based Nursing. 21, 7-8.

Leung, L. (2015) Validity, reliability, and generalizability in qualitative research. Journal of Family Medicine and Primary Care. 4 (3), 324-327.

Melnikovas, A. (2018) Towards an Explicit Research Methodology: Adapting Research Onion Model for Futures Studies. Journal of Futures Studies. 23 (2), 29-44.

Paez, A. (2017) Grey literature: An important resource in systematic reviews. Journal of Evidence Based Medicine. 10 (3), 233-240.

Sahay, A. (2016) Peeling Saunder’s Research Onion. Available from's_Research_Onion [Accessed 2 May 2019].

Saunders, M. and Tosey, P. (2013) The Layers of Research Design. Available from [Accessed 13 May 2019].

Saunders, M., Lewis, P., and Thornhill, A. (2011) Research Methods for Business Students. Pearson, New York.

Tashakkori, A., & Creswell, J. W. (2007). Exploring the nature of research questions in mixed methods research. Journal of Mixed Methods Research. 1 (3), 207-211.

Zalaghi, H. and Khazaei, M. (2015) The role of deductive and inductive reasoning in accounting research and standard setting. Asian Journal of Finance and Accounting. 8 (1), 23-37.