Critical Review and Assessing Evidence


If you are thinking about carrying out your own research then you will need to undertake an evidence review. This involves searching for, reading, and evaluating existing documents related to your area of research. The scale and depth of your evidence review will vary depending on the size of your research project, however, the process of reviewing evidence is the same.

Why should you read existing research?

Reading and evaluating existing research is necessary because, as a researcher, you need an understanding of your field of research: what is already known, how this has been researched, and what the key issues are. You need to know how the main theories in your research area have been developed and applied, and also any criticisms of work in this area. In addition, conducting an evidence review will:

  • provide the context for your own research
  • enable you to determine the extent to which your research question has been addressed previously
  • allow you to assess what gaps in knowledge exist and what the potential impacts are
  • highlight areas that need further development or a different approach

Sources of information

Books can provide a good general introduction to a topic, although research findings will quickly become outdated in books. Journals are probably the most useful resource as they publish the most current and ground-breaking research. The research contained in a journal has also usually been subject to peer-review. Increasingly, journal publications are being published with open access, and most peer-reviewed journals are available online as well as in print.

The internet is also an invaluable source when searching for research and evidence, however, it is important to note that the information has not been subject to the same quality control processes that officially published evidence has. In addition to journals and e-books, you can also find many official publications, including guidelines, standards, policies and statistics available in full and free to download, for example:


What is an evidence / literature review?evaluating evidence process diagram

Broadly speaking, conducting an evidence review means identifying and evaluating what is known about a topic. An evidence review is an essential stage in any research project as it provides the context, explaining the relevance of the research, and also helps to identify the main research question(s). 

There are different types of evidence and literature reviews but the type of review you are most likely to be familiar with is known as a ‘stand-alone review’. These are often ‘systematic reviews’, which review existing evidence in order to determine ‘what works best’. A formal systematic review follows a robust methodology and reporting format, but less systematic literature reviews can also provide useful information to inform your ideas.

All evidence reviews need to be well-structured and pre-planned. In particular, you need to clearly describe the methods used for identifying and evaluating evidence and you should have well defined search parameters and explicit inclusion and exclusion criteria.




This section will provide an overview of the following:

  • How to search for evidence
  • Critical review and evaluation of evidence
  • Managing and referencing
  • Peer review

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