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Systematic Reviews

Specialised advice for planning, researching and writing Systematic Reviews.

Synthesis

Synthesis /'sInθ…ôsiz/ /'sinthuhseez/

The combination of parts or elements, as material substances or objects of thought, into a complex whole

The Macquarie Dictionary (6th ed.).


Synthesis is a stage in the systematic review process where extracted data are pooled together and evaluated.

 

It is one of the most important stages of the systematic review process, as it determines the outcomes of the review.

 

There are two commonly accepted methods of synthesis in systematic reviews:

 

  • Quantitative data synthesis
  • Qualitative data synthesis

 

This division is not absolute, and even when conducting a quantitative systematic review, aspects of qualitative data synthesis are relevant in explaining why studies have been excluded or differ from the findings of the meta-analysis.

 

Adapted from the Monash University Systematic Review libguide.

Quantitative data synthesis

In a quantitative systematic review, which explores similar studies, data will be processed through a meta-analysis. During meta-analysis, data from different studies are weighted depending on their sample size and relevant criteria, and evaluated to determine the cumulative outcome. The results of a meta-analysis are most frequently represented in a Forest plot. (See side box).

Adapted from the Monash University Systematic Review libguide.

Qualitative data synthesis

In a qualitative systematic review, data will be synthesised by comprehensive critical appraisal through either a meta-study or a meta-synthesis.

  • A meta-study is a specific research approach in which the theory, methods and findings of qualitative research are analysed and synthesised to develop new ways of thinking about a topic.
  • A meta-synthesis uses interpretive methods to synthesise the findings from primary studies, which can often vary in important respects (such as populations or settings), to produce new insights and understandings.

Neither of these methods involves the reanalysis of raw data from the primary qualitative studies.

Both meta-studies and meta-syntheses can be used to determine what is known and what is not known, reflect on the processes and perspectives of the relevant body of research, explore the underlying methodological decisions and theoretical influences, and suggest future directions for researchers, theoreticians and clinicians.

Adapted from the Monash University Systematic Review libguide.

Forest Plots

For a meta analysis, producing a forest plot may be necessary.

Synthesis tools

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