Mathematics
Error Terms in Regression Analysis
Quick fact
The error term is a central concept in regression: it represents the aggregate of all factors that affect the outcome but are not explicitly included in the model, ranging from measurement error to genuinely random variation.
Why this is interesting
Every statistical model is a simplified story about the world, but what happens to the parts of the story that don't fit? The error term is the 'rest of the story'—the invisible influence that makes our predictions imperfect.