"Dear Mei Yi,
I am afraid that I don't know any simple guidelines. If fact, I don't think that it is easy to derive such guidelines. There are a couple of factors affecting it. For example, the no. of variables, the percentages of missing…"
"Dear Mei Yi Ng & Katherine,
It is not easy to give a simple rule. You may consider a random-effects meta-analysis as a simple analysis in estimating the means and covariance matrix of the effect sizes.
There are 7 variables in your model. Thus,…"