Residual
SAT glossary · Math
Definition
Actual minus predicted. A positive residual puts the point above the line and means the model under-predicted; a negative residual means it over-predicted.
Residual in plain English
A residual is simply the difference between what actually happened and what a model PREDICTED would happen: residual=actual-predicted. If a residual comes out positive, that data point sits ABOVE the line of best fit, meaning the model guessed too LOW for that point (under-predicted). If it's negative, the point sits BELOW the line, meaning the model guessed too HIGH (over-predicted). Residuals are basically a report card for how well your model is doing at each individual point.
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