Calling all interested meta-analysts
I note with interest the instructive paper 'Simpson's paradox and calculation of number needed to treat from meta-analysis' published in Biomed Central
(http://www.biomedcentral.com/1471-2288/2/1).
In order that I may gain a better understanding of the paper, I would be most grateful to receive an explanation of how the weights listed in Figure 1 of this paper have been calculated. I have tried to replicate the values using the inverse of the variance for the risk difference for the first two studies and thus using the inverse of the values 0.039 and 0.013, respectively. I am assuming the methodology for calculating the variance of a risk difference provided at http://www.childrens-mercy.org/stats/model/metaanalysis.asp
Can you please clarify why I obtain different results from the authors.
I have already contacted the first author regarding this but have received no reply as yet.
Many thanks
Best wishes
Margaret
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