# Standard error for difference between two independent gains

I've calculated an effect size for the difference between two standardized pre-post differences of two independent groups of subjects.

That is: $$[Mean_{dif_{group~1}}/SD_{dif_{group~1}}]-[Mean_{dif_{group~2}}/SD_{dif_{group~2}}]$$

where $$Mean_{dif}$$ is the difference between the means of pre- and post-tests of each group. And $$SD_{dif}$$ is the standard deviation of the difference scores for each of the two independent groups.

I was wondering what is the standard error of this effect size?

P.S1: This effect size also appears in Table 1 (row 5), p. 114 of this article. The same article, however, doesn't seem to provide the sampling variance of this effect size in Table 2, on p. 117.

P.S2: This answer provides an SEM solution to obtain SE for pre-post differences in only one group of subjects.

• Does this help stats.stackexchange.com/questions/256053/… – mdewey May 5 at 11:02
• @mdewey, unfortunately that article doesn't provide any direct insights. But Table 1 and Table 2 of this article does provide some better insights. – rnorouzian May 5 at 13:30
• It should be straightforward to extend it to multiple-group analysis in SEM if you have the required means and covariance matrices. – Mike Cheung Jun 8 at 6:56