# Meta Regression- Average AGe

I want to conduct a meta-regression, using the variable. The studies in my meta-analysis include studies, that compore two indipendent groups. My question: to calculate average age of a study - is it enough to simply to add up the age of the two indipendent groups and divided it by two? Or are there any other, better ways to get the average age?

• That will give you the average age. But what do you want to do with the average age when you've calculated it? Sep 23, 2019 at 16:15
• I would like to use it as a moderator variable, in a meta-regression. Sep 23, 2019 at 16:22
• and the two samples are usually not the same size, I guess thats a problem Sep 23, 2019 at 16:41
• I found the right solution in the meantime Sep 23, 2019 at 16:58
• Xa= population size of group A Ya= average of group A Xb= population size of group B Yb= average of group B (Xa/(Xa+Xb))*Ya + (Xb/(Xa+Xb))*Yb = Yc (the average of the combine population) Sep 23, 2019 at 16:59

$$\frac{n_1 \bar{x_1} + n_2 \bar{x_2}}{n_1 + n_2}$$ where $$n$$ is a sample size and $$\bar{x}$$ is a mean.