Using the Fit Line command, you can add straight line fits to your scatterplot using least squares regression. Using the Fit Polynomial command, you can fit polynomial curves of a certain degree using least squares regression.
Example of Fit Line and Fit Polynomial 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.
