Question
However, we do have conditional exchangeability in the data. This is because, when we condition on 𝑋 , there is no longer any non-causal association between 𝑇 and 𝑌 . The non-causal association is now “blocked” at [...](where? variable?) by conditioning on 𝑋 . We illustrate this blocking in Figure 2.4 by shading 𝑋 to indicate it is conditioned on and by showing the red dashed arc being blocked there