I think here the correction applies to each part of the equation separately, with \(df = n_T - 1\) and \(df = n_C - 1\), respectively.

Maybe it is also good to point out that this formula is only an approximation and an exact solution exists (see Morris 2000 for a comparison)

This should be Eq 24!?

Are there any reasons to drop the term \(\frac{n_T + n_C - 2}{n_T + n_C - 4}\) from Eq 24, Morris and to replace the last term \(\frac{d^2}{c^2}\) by \(d^2\)?

this should read \(d_{PPC1}\)