Publication Bias

Publication Bias:

•The publication or non-publication of research findings, depending on the nature and direction of the results (ref. Cochrane Handbook)

•Publication bias exists when the studies included in the analysis differ systematically from all the studies that should have been included.

•Typically, studies with larger than average effects are more likely to be published and this can lead to upward bias in the summary effect

•Publication bias is when studies with positive findings are more likely to be published 

•This means that any meta analysis or literature reviews based only on published data will be biased, so researchers should make sure to include unpublished reports in their data as well

Funnel Plot: 

•Plots of “trials’ effect estimates”against“sample size”

•Funnel plot is based on the fact that precision in estimating underlying treatment effect will increase as sample size of component studies increases

•Results from small studies will scatter widely at bottomofgraph, with spreadnarrowing among larger studies

•In absence of biasplot will resemble a symmetrical inverted funnel

•Conversely, if there is bias, funnel plots will often be skewed and asymmetrical

•Symmetry (or asymmetry) - visual examination(so it is subjective)

PSM / COMMUNITY MEDICINE by Dr Abhishek Jaiswal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
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