one-step method of moment estimate of between random effect variance
implementation follows Kacker 2004 and DerSimonian and Kacker 2007 eq. 6
- Parameters:
- eff
ndarray
effect sizes
- var_eff
ndarray
variance of effect sizes
- weights
ndarray
weights for estimating overall weighted mean
- Returns:
- tau2
float
estimate of random effects variance tau squared