Figure 1.

Plot of bias against magnitude of unmeasured confounding Δ using 2SPS method:(a) P (R = 1) = 0.8, ρ_a = 0, ρ_c = 0.5, ${\theta }_c^1=3.33$, ${\theta }_c^0=1.67$. (b) P (R = 1) = 0.8, ρ_a = 0, ρ_c = 0.8, ${\theta }_c^1=3.33$, ${\theta }_c^0=1.67$. (c) P (R = 1) = 0.8, ρ_a = 0, ρ_c = 0.5, ${\theta }_c^1=33.3$, ${\theta }_c^0=16.7$. (d) P (R = 1) = 0.5, ρ_a = 0, ρ_c = 0.8, ${\theta }_c^1=3.33$, ${\theta }_c^0=1.67$. The different colour of solid line corresponds to different shape parameter: black (α = 0.5), red (α = 1), and green (α = 2).