Research Guides: Evidence Synthesis: Step 6: Analysis & Synthesis

Qualitative Synthesis

Most evidence synthesis projects contain qualitative data in addition to--or sometimes instead of--quantitative data. In this case, the extracted data should be analyzed and synthesized using qualitative methods. The chart below from Schick-Makaroff et al. (2016) summarizes some different categories of research synthesis methodologies.

Types of Research Synthesis	Definition	Data Types Used	Products	Examples
1. Conventional Synthesis	Older forms of review with less-systematic examination, critique, and synthesis of the literature on a mature topic for re-conceptulization or on a new topic for preliminary conceptualization	Quantitative studies Qualitative studies Other types of data e.g., theoretical literature, policy	Narrative expression and summary Tables, charts, graphical displays, diagrams and maps Theory, theoretical/conceptual frameworks, or conceptual maps	Integrative review [14],[18]–[21] Narrative synthesis [16] Conventional literature review[17]
2. Quantitative Synthesis	Combining, aggregating, or integrating quantitative empirical research with data expressed in numeric form	Quantitative studies	Narrative expression and summary Mathematical scores Statements of generalizability	Systematic review [13],[26]–[27] Meta-analysis [22]–[25] Best evidence synthesis [28]–[30]
3. Qualitative Synthesis	Combining, aggregating, or integrating qualitative empirical research and/or theoretical work expressed in narrative form	Qualitative studies Other types of data e.g., theoretical literature	Narrative expression and summary Theory, theoretical/conceptual frameworks, or conceptual maps A definition	Meta-synthesis [31]–[44] Concept analysis [45]–[47] Grounded formal theory [37],[48]–[52] Meta-study [31],[37],[48]–[50],[53]–[54] Meta-analysis [37]–[38],[55]–[58] Meta-interpretation [59] Meta-ethnography [49]–[50],[60]–[62]
4. Emerging Synthesis	Newer syntheses that provide a systematic approach to synthesizing varied literature in a topic area that includes diverse data types	Quantitative studies Qualitative studies Other types of data e.g., theoretical work, grey literature, editorials, commentaries, policy, evaluations	Narrative expression and summary Tables, charts, graphical displays, diagrams and maps Mathematical scores Theory, theoretical/conceptual frameworks, or conceptual maps A report written for decision-makers	Scoping review [63] Rapid review [64]–[65] Rapid realist review [66] Meta-narrative synthesis [67]–[68] Realist synthesis [68]–[69] Meta-summary [70] Critical interpretive synthesis [71]–[74] Other types of mixed-research synthesis [49],[72],[75]–[79]

What synthesis methodology should I use? A review and analysis of approaches to research synthesis
Schick-Makaroff, K., MacDonald, M., Plummer, M., Burgess, J., & Neander, W. (2016). What synthesis methodology should I use? A review and analysis of approaches to research synthesis. AIMS Public Health, 3(1), 172–215. https://doi.org/10.3934/publichealth.2016.1.172
Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline
Campbell, M., McKenzie, J. E., Sowden, A., Katikireddi, S. V., Brennan, S. E., Ellis, S., Hartmann-Boyce, J., Ryan, R., Shepperd, S., Thomas, J., Welch, V., & Thomson, H. (2020). Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline. BMJ (Clinical Research Ed.), 368, l6890. https://doi.org/10.1136/bmj.l6890

Meta-Analysis

If all the studies included in your evidence synthesis project are quantitative, it may be appropriate to conduct a meta-analysis, a statistical combination of previously conducted quantitative studies. The chart below from Paul and Barari (2022) compares meta-analysis to traditional systematic literature reviews.

Differences	Traditional SLRs	Meta-analysis
What	A qualitative process for assembling, arranging, and assessing existing literature in a research domain.	A quantitative method that integrates the results of empirical studies to provide an aggregate summary of findings in a research domain.
Why	Providing a comprehensive picture of what is known and proposing directions for future research based on what is not known in that research domain.	To achieve statistically precise and accurate conclusions about the strength and direction of a relationship between variables and moderator role in a research domain.
When	The research topic is evolving to allow a researcher to provide a current view of what is known and define the future direction of the research domain.	The research topic is mature enough to allow a researcher to provide an overall picture of relationships and the role of moderators in a research domain.
Where	Include all types of relevant studies from high-quality journals through subjective selection and interpretation of data to synthesize the findings of prior studies in a systematic manner.	Include published and unpublished studies that empirically examine the relationships of interest through objective and rigorous statistical procedures to synthesize the findings of prior studies and test hypotheses that have not been studied in prior research.
How	Through SLRs process include defining a research question, data collection, data preparation, data analysis, and reporting and using the SLRs approach, that is, domain-based reviews, theory-based reviews, and method-based reviews.	Through meta-analysis process include defining the research question, data collection, data preparation, data analysis, and reporting and meta-analysis approach, that is, main model and moderator analysis.

Meta-analysis and traditional systematic literature reviews—What, why, when, where, and how?
Paul, J., & Barari, M. (2022). Meta‐analysis and traditional systematic literature reviews—What, why, when, where, and how? Psychology & Marketing, 39(6), 1099-1115. https://doi.org/10.1002/mar.21657
What is a meta-analysis?
Shorten, A., Bratches, R., & Shorten, B. (2025). What is a meta-analysis? Evidence-Based Nursing, 28(2), 74-76. https://doi.org/10.1136/ebnurs-2024-104230
A 24-step guide on how to design, conduct, and successfully publish a systematic review and meta-analysis in medical research
Muka, T., Glisic, M., Milic, J., Verhoog, S., Bohlius, J., Bramer, W., Chowdhury, R., & Franco, O. H. (2020). A 24-step guide on how to design, conduct, and successfully publish a systematic review and meta-analysis in medical research. European Journal of Epidemiology, 35(1), 49–60. https://doi.org/10.1007/s10654-019-00576-5