Ecological correlation refers to a type of [[Correlation]] that is observed when data is collected and analyzed at a group level, rather than at the individual level. **Example:** - You look at the correlation between average income and the average life expectancy per country. - It can happen that the correlation on aggregated country level is overstating or understating the correlation on individual level. **Effects:** - *Overstated correlation:* The variability of the effect on individual level is smoothed by the averaging. - *Understated correlation:* Contextual variables on the aggregated level dilute the correlation on individual level.