Table 3:

Design effects for sample size formula (10). $r_{a_1}=P\left(R^{\left(a_1\right)}=1\right)$ is the response rate to first-stage treatment a₁.

Design	Design effect	Conservative design effect
I	2	2
II	$\frac{1}{2}\left(2-r_1\right)+\frac{1}{2}\left(2-r_{-1}\right)$	2
III	$\frac{1}{2}\left(3-r_1\right)$	$\frac{3}{2}$