What is a fitted regression line?

A fitted regression line on a graph represents of the mathematical regression equation for your data. Use fitted regression lines to illustrate the relationship between a predictor variable (x-scale) and a response variable (y-scale) and to evaluate whether the model fits your data.

Fitted regression line illustration

Fitted regression lines are drawn using the least squares estimation method which minimizes the sum of the squared distances between the points and the fitted line.

A regression fit line can be drawn to fit a linear, quadratic, or cubic model.


Example of using fitted regression lines to determine the model

You are studying the relationship between a particular machine setting and the amount of energy consumed. You suspect that this relationship has curvature, but you need to confirm and document the curvature. You produce the following plots:


The quadratic model appears to fit the data better than a linear model.

Add a fitted regression line to a graph

Fitted regression lines can be added to graphs such as scatterplots and matrix plots.

  • To add or edit a fitted regression line when you create a graph, in the dialog box for the graph you are creating, click Data View, and choose the Regression tab.
  • To add a fitted regression line to an existing graph, right-click the graph and choose Add > Regression Fit.
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