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Conducting a Literature Review

A collection of strategies and resources for conducting a literature review

Analyzing the Literature

Evidence synthesis and critical appraisal are two distinct but interrelated processes in the field of evidence-based practice and research. Here's a breakdown of the differences between them:

Critical Appraisal:

  • Definition: Critical appraisal involves systematically evaluating the quality, relevance, and validity of research studies or evidence sources. It aims to assess the strengths and weaknesses of individual studies to determine their trustworthiness and applicability to a particular research question or clinical scenario.
  • Focus: Critical appraisal focuses on examining the methodology, design, data analysis, and results of research studies. It involves assessing factors such as study design, sample size, bias, confounding variables, statistical methods, and generalizability.
  • Purpose: The purpose of critical appraisal is to identify high-quality evidence that can inform decision-making in healthcare practice, policy, or research. It helps researchers and practitioners assess the credibility and reliability of evidence sources and make informed judgments about their use in practice.

Evidence Synthesis:

  • Definition: Evidence synthesis involves systematically collecting, analyzing, and integrating evidence from multiple sources to generate new knowledge, insights, or conclusions about a particular topic or research question. It aims to aggregate and synthesize findings from individual studies to produce a comprehensive summary of the available evidence.
  • Focus: Evidence synthesis encompasses a variety of methods, including systematic reviews, meta-analyses, scoping reviews, and narrative reviews. It focuses on synthesizing data, findings, and conclusions from multiple studies to provide a comprehensive overview of the evidence base on a particular topic.
  • Purpose: The purpose of evidence synthesis is to provide stakeholders with a robust and comprehensive summary of the existing evidence on a particular topic or research question. It helps identify patterns, trends, inconsistencies, and gaps in the literature, informing decision-making, guiding policy development, and identifying future research priorities.

In summary, critical appraisal involves assessing the quality and validity of individual research studies, while evidence synthesis involves aggregating and synthesizing findings from multiple studies to generate new knowledge or insights about a particular topic. While they are distinct processes, they are often conducted sequentially, with critical appraisal informing the selection and inclusion of studies in evidence synthesis. Together, critical appraisal and evidence synthesis play essential roles in evidence-based practice and research, 

Critical Appraisal

Conducting a critical appraisal of the literature is crucial for evidence-based practice for several reasons:

  • Validity and Reliability: It helps you assess the quality of the evidence you're using, ensuring that you can trust the findings and apply them to your practice confidently.
  • Informed Decision-Making: By critically appraising the literature, you can make informed decisions about which studies are most relevant and appropriate to inform your practice, ensuring it's based on the best available evidence.
  • Identifying Gaps and Limitations: This process allows you to spot gaps and limitations in the existing literature related to your practice area, helping you refine your clinical questions and design more robust interventions.
  • Applicability to Practice: You aim to implement evidence-based practices to improve patient outcomes. Critical appraisal helps you assess how applicable the literature is to your clinical setting, considering factors like patient population and available resources.
  • Ethical Considerations: Ethical principles are crucial in healthcare practice. Critical appraisal helps you evaluate whether the studies you're using adhere to these principles, ensuring your practice respects patient autonomy, beneficence, and non-maleficence, and avoids bias.

By conducting a critical appraisal of the literature, you ensure that your evidence-based practice is grounded in high-quality evidence, aligns with ethical standards, and has the potential to positively impact patient care outcomes.

Synthesizing the Articles

Literature reviews synthesize large amounts of information and present it in a coherent, organized fashion. In a literature review you will be combining material from several texts to create a new text – your literature review.

You will use common points among the sources you have gathered to help you synthesize the material. This will help ensure that your literature review is organized by subtopic, not by source. This means various authors' names can appear and reappear throughout the literature review, and each paragraph will mention several different authors.

When you shift from writing summaries of the content of a source to synthesizing content from sources, there is a number things you must keep in mind:

  • Look for specific connections and or links between your sources and how those relate to your thesis or question.
  • When writing and organizing your literature review be aware that your readers need to understand how and why the information from the different sources overlap.
  • Organize your literature review by the themes you find within your sources or themes you have identified. 

You can use a synthesis chart to help keep your sources and main ideas organized. Here are some examples:

California State University, Northridge. (2017). Literature Review How-To: Synthesizing Sources. Retrieved from

Things to Think About

Before you begin to analyze and synthesize the articles you have selected, read quickly through each article to get a sense of what they are about. One way to do this is to read the abstract and the conclusion for each article.

It is also helpful at this stage to begin sorting your articles by type of source; this will help you with the next step in the process. Many papers (but not all) fall into one of two categories:

  • Primary source: a report by the original researchers of a study.
  • Secondary source: a description or summary of research by somebody other than the original author(s), like a review article.

These are a selection of questions to consider while reading each article selected for your literature review. 

Primary Sources:

  • Title
  • Author and Year
  • Journal
  • Purpose of Study
  • Type of Study
  • Setting
  • Data Collection Method
  • Major Findings
  • Recommendations
  • Key thoughts/comments (eg. strengths and weaknesses)

Secondary Sources (ie. reviews)

  • Title
  • Author and year
  • Journal
  • Review questions/purpose
  • Key definitions
  • Review boundaries
  • Appraisal criteria
  • Synthesis of studies
  • Summary/conclusions
  • Key thoughts/comments (eg. strengths and weaknesses)

Cronin, P., Ryan, F., & Coughlan, M. (2008). Undertaking a literature review: A step-by-step approach. British Journal of Nursing, 17(1), 38-43. Retrieved from:

When Am I Done?

You are done with your literature review synthesis when :

  • You are not finding any new ideas,
  • When you encounter the same authors repeatedly, and/or
  • When you feel that you have a strong understanding of the topic
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