Once you have decided which articles to include in your review, you need to extract relevant data from those studies. This should be done in a structured and systematic way and is usually presented in tables in the final review report.
Tips:
Data can mean any information from a study including:
NVivo software may be helpful for systematic reviews with qualitative data.
You can extract your data into a simple table, but if you want a more detailed approach there are a number of analysis tools that can help:
The following links can also give guidance.
Guidance from the Centre for Reviews and Dissemination for creating a textual summary of the relevant studies and analysing their robustness.
Also produced by CRD this link covers doing a statistical analysis of the combined results of the relevant studies.
Cochrane Handbook – Chapter 5: Collecting data. See especially Table 5.3a: Checklist of items to consider in data collection
Centre for Reviews and Dissemination. (2009, January). Systematic reviews: CRD's guidance for undertaking reviews in health care. University of York. https://www.york.ac.uk/media/crd/Systematic_Reviews.pdf
(See Section 1.3.3 Data extraction, pp 28-32, Section 1.3.5 Data synthesis, pp. 45-76).
Crombie IK, Davies HT. What is meta-analysis? [Internet]. Bandolier.org.uk; 2009.
Barnett-Page. E, & Thomas, J. (2009). Methods for the synthesis of qualitative research: A critical review. BMC Medical Research Methodology, 9(59).
Elamin, M. B., Flynn, D. N., Bassler, D., Briel, M., Alonso-Coello, P., Karanicolas, P. J., Guyatt, G. H., Malaga, G., Furukawa, T. A., & Kunz, R. (2009). Choice of data extraction tools for systematic reviews depends on resources and review complexity. Journal of Clinical Epidemiology, 62(5), 506-510. https://doi.org/10.1016/j.jclinepi.2008.10.016