Residuals
The vertical distance from each data point to the regression line, calculated as ei = yi - ŷi, where ŷi = a + bxi is the predicted value.
Real World
Netflix analysts calculate residuals when fitting a regression line to predict viewing hours from subscriber age — large positive residuals flag age groups watching far more than the model predicted.
Exam Focus
Always state the residual formula e = y − ŷ and show your substitution clearly for method marks.
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