Formula for the standard error of a Cohen's d
According to p238 of standard text on meta-analysis in social science The Handbook of Research Synthesis, the variance of Cohen's d is
( [(n1 + n2)/(n1*n2)] + d2 / 2*(n1 + n2 − 2) )*([n1 + n2] / [n1 + n2 − 2] ),
where n1 and n2 are the sample sizes of the two groups being compared and d is Cohen's d .
Taking the square-root of this variance gives the standard error of d , needed as input by several of the user-written meta-analysis packages for Stata. (Some of them also accept confidence intervals as input, but they simply convert them to standard errors internally anyway.)