Statistics help with a meta-analysis?

I do not have any experience doing statistics with data from a meta-analysis. However, I am working on a research project at the moment where I must look for a significant difference between groups in the meta-analysis. But my project advisor is off at the moment and I would like to begin this part of the project before he returns. So, I was wondering if someone with experience doing meta-analyses can help me?

There are 3 groups in this meta-analysis (group A,B and C). Each group has a different population and different number of people in each group. Each study in the meta-analysis gives me a proportion of individuals with Thyroid cancer for each group (A,B and C). I would like to find if there is a significant difference in prevalence of Thyroid cancer between the 3 groups. I am a bit confused about how to do this? Do I use a T-test to find the sig. difference in each individual study? Do I find the weighted average of the proportions in each group (ie averaging out the proportions for each study in each of the 3 groups) and then do the t-test? Would it be best to use another statistical test?

@mdewey I have about 50 studies in the meta-analysis. Not all of them use the exact same 3 groups. Some only use one of the groups and others use all 3 (none of them use 2 groups). I have the proportions for each study and group in the study. For example, if a study has 3 groups, then I will have a proportion for each of the groups. I would like to find out if there's an overall significant difference in proportions between the 3 groups.

• Do you mean you have a number of primary studies each of which used exactly the same three groups? Do you have just the proportions or do you have numerator and denominator? Feb 25, 2017 at 16:47
• @mdeweyI have about 50 studies in the meta-analysis. Not all of them use the exact same 3 groups. Some only use one of the groups and others use all 3 (none of them use 2 groups). I have the proportions for each study and group in the study. For example, if a study has 3 groups, then I will have a proportion for each of the groups. I would like to find out if there's an overall significant difference in proportions between the 3 groups. Feb 25, 2017 at 17:16
• In a meta-analysis, you pick one hypothesis - that's comparing two groups. Then you find the estimate of the difference between the groups (possibly standardized) and its standard error. You don't do a t-test. Feb 25, 2017 at 19:01
• @JeremyMiles But how does that tell you if there is a significant difference? Feb 25, 2017 at 20:45
• Your comment which someone has kindly edited into the question for you does not answer all my question. Do you have the absolute frequencies or just proportions? Feb 26, 2017 at 12:40

Having said all that you are studying thyroid cancer and although this has a good prognosis none the less human lives may be at stake here and I think you should consider getting expert help locally as if you thought that a $t$-test might work here you may need some more help than we can give you on a question and answer site.