# How to calculate Inverse variance weight of several pearsons r correlations

I have a set of pearsons r effect sizes , converted to fishers z scores for meta analysis. I am wondering what data I need to calculate an inverse variance weight for each effect size and how I calculate these please? Also , is there an easy online calculator or spss method for doing this?

Thanks

I you have the sample sizes, which I assume you do then the standard error is

$$\frac{1}{\sqrt(N-3)}$$

So to get the sampling variance you just square that.

$$\frac{1}{(N-3)}$$

• Thanks mdewey. Am I correct in thinking that I need to use the above formulas for each individual effect size (not a total or average of all) while in the form of a fishers z score please? Aug 4, 2018 at 14:31
• Yes, for each one. Aug 4, 2018 at 15:24
• Also , I have two different sample sizes related to two correlations ( both averaged in fishers z) in one article as it uses two studies within it. Is it acceptable to calculate an average of the two sample sizes for the standard error and inverse variance calculation please? Aug 4, 2018 at 19:09
• Hi mdewey - when you say "So to get the sampling variance you just square that" - do you mean N as in sample size or the calculated standard error please? Aug 4, 2018 at 19:53
• Yes, it is the sample size. Aug 5, 2018 at 8:50