## Adjusted indirect comparisons: Algebra [General Sta­tis­tics]

Dear Helmut,

» ... The error term in the 2×2×2 crossover is given by $$SE_\textrm{(d)}=SE_\Delta=\widehat{\sigma}_\textrm{w}\sqrt{\frac{1}{n_\textrm{1}}+\frac{1}{n_\textrm{2}}},\tag{2}$$where $$\small{\widehat{\sigma}_\textrm{w}=SD_\textrm{w}=\sqrt{MSE}}$$ from ANOVA. Alternatively we can write $$SE_\Delta=\sqrt{\frac{SD_{\textrm{w}}^{2}}{2}\left (\frac{1}{n_\textrm{1}}+\frac{1}{n_\textrm{2}}\right )}\tag{3}$$
Here I can't follow you. From where arises the 2 in formula (3)

Regards,

Detlew