Regression

Statistics — Third Secondary

Prediction and its limits

We use the regression equation to predict the value of y that corresponds to a known value of x.
Two kinds of prediction must be distinguished:

Interpolation (prediction inside the data range) the value of x lies between the smallest and largest x-values used to build the line. The result is usually reliable.
Extrapolation (prediction outside the data range) the value of x is larger or smaller than the values used. The result is less reliable and may even be impossible in real life.
The accuracy of prediction also depends on the strength of the correlation.
The closer r is to 1 or −1, the closer the points lie to the line, and the more accurate the prediction.

Regression · 3 / 7