Funnel plot, Advanced Statistics

It is an informal method of assessing the effect of the publication bias, generally in the context of the meta-analysis. The effect measures from each of the reported study are plotted on the x-axis against the corresponding sample sizes on y-axis. Because of nature of sampling variability this plot should, in the nonexistence of publication bias, have the shape of the pyramid with a tapering 'funnel-like' peak. Publication bias will tend to skew pyramid by selectively not including studies with small or no significant effects. Such studies predominate when sample sizes are small but are increasingly less ordinary as the sample sizes increase. Thus their absence removes part of the lower left-hand corner of the pyramid. This effect is illustrated in the Figure which is drawn below.

338_funnel plot.png

Posted Date: 7/28/2012 2:49:24 AM | Location : United States







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