There are a wide variety of formats your literature review can take, from the more traditional, narrative option to a systematic review with a meta-analysis of previous findings. Each are important in their own way and depending on your research question may be relevant.
Traditional literature reviews are similar to the introductions found in most journal articles, giving a broad background on the field. They delve into the current issues and concepts and allow the reader to gain a better understanding on potential knowledge gaps that future research could fill. There are a number of variations on the traditional literature review from an Argumentative approach to a Scoping view on the field as a whole, so it is important to decide on the route you want to take as it can impact the sources you choose.
If you wanted to take a more structured, evidence-based approach that includes previously published data a systematic review may be more appropriate. Medical research degrees usually opt for this option as defined criteria are used to determine the sources used and meta-analyses can be conducted with quantitative published data to show overall results in the field and potential new research questions. Systematic reviews are not as broad as traditional review styles, so certain ideas and findings may not be covered, but their increased focus allows for more detail on issues.
Rapid evidence reviews are usually used in policy and other industries to gather and interpret current information in the field in a short amount of time. It is not as detailed or broad as a systematic or traditional review but does follow similar search selection techniques as the systematic review.
We will now delve more into these three general review types, traditional, systematic and rapid evidence reviews in the upcoming sections.
Traditional reviews are a qualitative critical assessment of a personal selection of material, and can occur in different forms including:
Conceptual, which synthesises and critically assesses literature to see the way in which a particular issue is understood. The conceptual review might also examine how the issue is researched, how those understandings are produced.
State of the art, which examines the most recent contributions to a field or area of study in the light of its history of research. It particularly looks for trends, agreements, and debates.
Argumentative, examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. It should be noted that a potential for bias is a major shortcoming associated with argumentative literature review.
Scoping, which creates an agenda for future research through documenting what is already known and highlighting the gaps and blind spots.
And Traditional or Narrative, which like a scoping review positions a piece of research that has already been undertaken within the field.
As you can see, many of these styles overlap one another, but a traditional review is usually written at the end of a research degree whereas the others can be written at the start, highlighting the need for your research to be performed. Traditional reviews can by nature be biased as your choice of sources is personal and may push the review in a certain direction, so this is important to bear in mind.
Published traditional literature review examples:
A traditional literature review can be considered as biased in the sources chosen. A systematic review tries to remove bias whilst also specialising a literature search by defining strict criteria all sources must meet in order to be inclusive. This is usually done by multiple reviewers to further remove bias, and although it narrows the field can take longer than a traditional review as every paper that fits the criteria listed must be included.
A systematic literature review attempts ‘to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question’ (Cochrane, 2013). A meta-analysis is a statistical assessment of the data provided from multiple studies or sources that attempt to ask/answer the same question.
Medical research usually opts for a systematic review, due to criteria allowing for specification of the methodology used and thus specific healthcare questions for populations can be researched. This approach is also used if a meta-analysis is to be conducted using previously published data. It allows for validation as to which sources have been chosen and why, and meta-analysis can be conducted correctly to determine statistical significances.
Often, the PICO method is used. This defines criteria based on Patients/Populations, The Intervention used, Comparisons chosen, and the Outcome. Criteria can vary but you must justify the criteria you have used in the introduction to your literature review so that the reader can follow why certain ideas, locations or time periods have been omitted.
For instance, some disciplines are fast moving, so you can use time as a criterion, then you only must read back three years, five years or whatever seems relevant. Your topic might have a strong theme to guide your reading, for instance geographical location, historical period or type of participant. If you are doing a thesis on primary school aged students, for example, there’s probably very little point in reading literature on higher education. Methodology can be a strong way to determine your criteria. If you are doing a scientific study, there might be no point referencing a qualitative study – and vice versa. There are, of course, exceptions, but mixing methodologies must always be done with care.
The University of Exeter Lib guides have a fantastic short online module about systematic reviews if you decide this is the review type for you, and Coventry University run a Massive Open Online Course (MOOC) on this topic.
Published systematic review examples:
Published meta-analysis review example:
Published systematic review that includes a meta-analysis:
Rapid evidence assessments provide a more structured and rigorous search and quality assessment of the evidence than a literature review but are not as exhaustive as a systematic review. They can be used to gain an overview of the density and quality of evidence on a particular issue and support the commissioning of further research by identifying evidence gaps. This form of review is common in policy environments as information is needed quickly and is often done by academics who already have a lot of knowledge in that area. However, this can be a good way to start researching your topic and increasing your writing practise at the start of your research degree, especially if you plan to write your literature review at the end of your research degree.
Usually specifically looking to answer one or more focused questions, setting boundaries and criteria similar to a systematic review can be helpful in narrowing down your searching, and sorting your master list into categories as we discuss in later sections of this module can help in determining the depth and scope you plan to go to.
Like with systematic reviews, you must state the criteria you used to narrow your search in the beginning of your rapid evidence review so that you and others can understand your reasoning. Your final literature review for your research degree is unlikely to be a rapid evidence review due to the lack of breadth usually found but can be great starting point or small published review at the start or end of your project.
Rapid evidence reviews examples at gov.uk:
Discuss with your supervisors. Are you planning on publishing your literature review or is it a thesis introduction? Is one type of review better for the start of your PhD and another at the end? Use this template to make a pro and con list for each and read examples from your field to help you decide.
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