$\mathbf{N}$
Patients
Group 1
(Active Treatment)
Group 2
(Placebo)
Group 3
(No Treatment / Natural History)
$\Delta_{\text{Drug}}$
$\Delta_{\text{Placebo}}$
$\text{Baseline}$
$\text{Drug Effect} = G_1 - G_2$
$\text{Placebo Effect} = G_2 - G_3$