ext{treatment effect} + \underbrace{
  \Big(\overline{Y_T^0} - \overline{Y_U^0}\Big)
  }_\text{selection bias}$$`

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# Correlation is causation plus selection

`$$\text{Difference in Means} = \underbrace{
  \Big(\overline{Y_T^1} - \overline{Y_T^0}\Big)
  }_\text{treatment effect} + \underbrace{
  \Big(\overline{Y_T^0} - \overline{Y_U^0}\Big)
  }_\text{selection bias}$$`

The difference in means is a result of 2 processes:
- **Treatment:** The true causal effect of the treatment variable. (Taking Advil re