I would like to work on a meta-analysis project. I have kept 8 studies that satisfy my criteria and I'd like to continue with these. Their results are formed as odds ratios (OR) and confidence intervals (CI).
I read that I should convert them into log values and estimate the standard errors. I did this, but I don't know how to continue since all examples that I have seen are about trials and provide the accurate numbers of outcomes (i.e., before treatment, after treatment, or death/alive, etc.) while I have only ORs and CIs.
Could anyone help me, please? Also, please propose a free software capable of analyzing ORs and CIs.
Best Answer
Although I'm not strictly answering your question, I assume you want to calculate a mean effect size. Assuming you are using comparable studies you'll need the odds ratios, which you have, and their variances, which you can recover using the post above. The mean effect size is simply a weighted mean of individual effect sizes: $ES_{mean}=\frac{\sum\limits_{i=1}^kw_{i}ES_{i}}{ \sum{w_{i}^{n=k}}}$ where $ES_{i}$ and $w_{i}$ are the effect size and effect size weight for study i. The weight of each effect size is simply the inverse of the estimate's variance, or $w_{i}=\frac{1}{\sigma^{2}_{i}}$, hence the more precise the estimate, the more weight it carries. There are several R packages to conduct meta-analysis; a simple search should provide what you need.