Evidence-appraisal glossary
Average Treatment Effect
The average difference in outcome if everyone in a population received the treatment versus if no one did. It is the target quantity that many causal studies set out to estimate.
Also called: ATE, average causal effect.
The average treatment effect contrasts two hypothetical worlds for the same population, so it is defined through potential outcomes. Related quantities focus on subsets, such as the effect among those actually treated or the effect near a decision cutoff. Knowing which of these a study estimates matters, because a treatment can help the average person yet be measured only within a narrow group that a particular method can reach.
Read the full Reading the Evidence blog.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.