4.27 ATT: Average Effect of the Treatment on the Treated and the Control

  • ATE is often defined for subgroups (See types of treatment effects)
  • One subgroup are those exposed to the treatment.. the treated
  • Average Effect of Treatment on Treated (ATT): E[Yi1 - Yi0 | Di = 1]
  • Q: Which observations does that concern in our table?
  • Q: Why might we sometimes be interested in the ATT instead of the ATE? Think of real examples!


Unit Di (Aspirin: Yes/No) Yi1 (Pain | YesAspirin) Yi0 (Pain | NoAspirin)
Simone 1 0 ?
Julia 1 1 ?
Paul 0 ? 1
Trump 0 ? 0
Fabrizio 0 ? 0
Diego 0 ? 0