[R-meta] I2 interpretation for Multilevel meta-analysis with moderators

[Ivan Jukic]

Dear Wolfgang,

thank you for explaining this and providing an example – I really appreciate it.

Indeed, in the posts I linked, you made it clear that I2 meaning is not very intuitive (or even meaningful) in models with moderators. However, I would like to use it because these moderators are the most important thing in my analysis. I was thinking about just looking at I2 without moderators but these analyses are less meaningful for the story that I'm trying to tell. I'm now considering reporting both.

I get (77.747826 3.745411 18.506763) for res0 (i.e., model without moderators), and (67.8411969 0.5082705 31.6505327) for res1 (i.e., model with moderators).

After reading your response I'm now unsure what the numbers obtained by 100 * pmax(0, (res0$sigma2 - res1$sigma2) / res0$sigma2) actually mean? I get (48.97833 92.06504).

In your response, you interpreted this as "how much of the between-study and within-study heterogeneity is accounted for by the moderators". Based on these numbers, it seems like a lot of between- and within-study heterogenity is accounted for by the moderators. However, I can't interpret this in the same way by just looking at I2 for res0 and res1 (81.49% and 68.35%, respectively, OR even individual heterogeneity components from each model)? I guess I'm still missing something here.

Cheers,
Ivan