15.8 Hedges’ g from Cohen’s d

We can also directly correct Cohen’s d and thus generate Hedges’ g using the formula by Hedges and Olkin (Hedges and Olkin 1985):

\[g \simeq d\times(1-\frac{3}{4(n_1+n_2)-9}) \] This can be done in R using the hedges_g function with the following parameters:

  • d: The value of Cohen’s d
  • totaln: the total N in the study
hedges_g(d = 0.75, totaln = 50)
## [1] 0.7382199


Hedges, L, and Ingram Olkin. 1985. “Statistical Models for Meta-Analysis.” New York: Academic Press.