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Grey Literature in Meta-Analysis |
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In meta-analysis, researchers combine the results of individual studies to arrive at cumulative conclusions. Meta-analysts sometimes include "grey literature" in their evidential base, which includes unpublished studies and studies published outside widely available journals. Because grey literature is a source of data that might not employ peer review, critics have questioned the validity of its data and the results of meta-analyses that include it. The objective of this project was to examine evidence regarding whether grey literature should be included in meta-analyses and strategies to manage grey literature in quantitative synthesis.
Meta-analyses that exclude grey literature likely (a) over-represent studies with statistically significant findings, (b) inflate effect size estimates, and (c) provide less precise effect size estimates than meta-analyses including grey literature. Meta-analyses should include grey literature to fully reflect the existing evidential base and should assess the impact of methodological variations through moderator analysis. Key Words: meta-analysis; research design Conn, V., Valentine, J.C., Cooper, H.M., & Rantz, M.J. (2003). Grey literature in meta-analysis. Nursing Research, 52(4): 256-261. |