Using the Fit Line option, you can add straight line fits to your scatterplot using least squares regression. Using the Fit Polynomial option, you can fit polynomial curves of a certain degree using least squares regression.
Figure 5.8 Example of Fit Line and Fit Polynomial
Figure 5.8 shows an example that compares a linear fit to the mean line and to a degree 2 polynomial fit.
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The Fit Line output is equivalent to a polynomial fit of degree 1.
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The Fit Mean output is equivalent to a polynomial fit of degree 0.
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For details about the options in the Linear Fit and Polynomial Fit Degree menus, see Fitting Menus. For statistical details about this fit, see Fit Line.