. Author manuscript; available in PMC: 2010 Aug 25.

Published in final edited form as: Psychol Methods. 2008 Dec;13(4):314–336. doi: 10.1037/a0014207

Table 4.

Mean Potential Values and Average Causal Effects Under Ignorability

Proportions of principal strata	Mean potential outcome		Average causal effect given C
Proportions of principal strata	X = 0	X = 1	Average causal effect given C
π _n	μ_n0 = μ_0,0	μ_n1 = μ_0,1	γ_n = μ_0,1 − μ_0,0
π _f	μ_f0 = μ_0,0	μ_f1 = μ_1,1	γ_f = μ_1,1 − μ_0,0
π _b	μ_b0 = μ_1,0	μ_b1 = μ_0,1	γ_b = μ_0,1 − μ_1,0
π _a	μ_a0 = μ_1,0	μ_a1 = μ_1,1	γ_a = μ_1,1 − μ_1,0

Note. X = experimental (treatment) condition assignment status; C = principal stratum membership; n = never-improver; f = forward-improver; b = backward-improver; a = always-improver.