New to causal inference/discovery I am struggling with the maths. In an example from Brady Neal’s videos the treatment is taking a pill (T=1) or not (T=0) with the outcome that my headache disappears (Y=1) or not (Y=0). He says the individual causal effect is Yi(1)-Yi(0) = 1 . Can someone tell me please what are the units for the answer 1? Naively it looks like it should be disappearing headaches per pill which doesnt make much sense to me. Or is the causal effect unitless like percentage change? thanks very much

I havent tried anything but i cant see if it should have units or not.