Figure 3

Planning future studies. The graph shows twelve completed experiments across six years along with two contemplated future studies, a fourth phase 2 trial (δ ₄) and a second phase 3 trial (ϵ ₂). A phase 3 trial (ϵ ₁) was initiated following the sole positive phase 2 study (δ ₂). The result of this phase 3 trial was negative, discordant with the earlier phase 2 result. Now researchers must decide which study (or studies) to do next: Trust that the accumulated evidence is still sufficient to motivate another phase 3 or return to phase 2 in search of greater consistency and a potential explanation for the discordance between δ ₂ and ϵ ₁.