Extrapolation

Extrapolation is using a regression line to predict outside the range of x-values the data covered, where the pattern may no longer hold.

Extrapolation stretches a fitted line beyond the interval of explanatory values you actually observed, where there is no evidence the linear trend continues. Predictions there can be badly wrong because the relationship may bend, flatten, or reverse. For example, a line fit to children's ages 5 to 12 might predict a 40-year-old is 12 feet tall. Keep predictions within the observed range of the explanatory variable to stay on safe ground.

More regression and correlation terms, or browse the full statistics glossary.