The consistency equation links a unit’s observed outcome to the potential outcome matching its actual treatment. For unit i, T(i)=0 implies Y(i)=Y₀(i), while T(i)=1 implies Y(i)=Y₁(i). Potential outcomes remain partly unobserved: each patient reveals only the outcome corresponding to the treatment received. section 10.1.1
Patient recovery
Suppose Holden receives treatment, T=1, and has observed recovery Y=1. Consistency identifies that observed recovery with Holden’s treated potential outcome, Y₁=1. Avasarala does not receive treatment, T=0, so observed recovery Y=1 corresponds to Y₀=1. The unreceived alternative outcome remains unknown for each patient. section 10.1.1
Table 10.1 Hypothetical example of POs with assignment (T(i)) and observed recovery (Y(i))
|
Name
|
i
|
Y
0(
i)
|
Y
1(
i)
|
T(
i)
|
Y(
i)
|
|---|---|---|---|---|---|
|
Drummer
|
1
|
0
|
0
|
1
|
0
|
|
Burton
|
2
|
1
|
0
|
1
|
0
|
|
Holden
|
3
|
0
|
1
|
1
|
1
|
|
Avasarala
|
4
|
1
|
1
|
0
|
1
|
Use the hypothetical patient table to compare potential outcomes, treatment assignment, and the resulting observed outcome. section 10.1.1
The equation is useful because it replaces the observed treatment-group potential outcome with measurable data when estimating causal effects. It supports adjustment and instrumental-variable formulas, and helps identify the treated term in ATET estimation; it does not reveal the missing counterfactual by itself. section 10.1.1 section 11.4.4
