How to Perform a Cubic Regression
If a cubic polynomial is a good fit for the data on a scatter plot, you need to perform a cubic regression. You can do this in the TINspire Lists & Spreadsheets application. To perform a regression, follow these steps:

Press
to move back to the Lists & Spreadsheet page containing the data needed.

Press [MENU]→Statistics→Stat Calculations→Cubic Regression.
A dialog box opens. As with any dialog box, you can press [TAB] to move from one field to the next or [SHIFT][TAB] to move backward through the fields. Press [ENTER] at any time for the configuration to take effect.
Notice in the first screen that pressing [CLICK] and selecting year enables you to specify the location of the X List. You could also specify the column by its letter reference. In the second screen, pressing [D][CTRL][ ( ] enables you to indicate where you want the results to be stored. Column D because it is the first available empty column.
The third and fourth screens (with columns D and E widened) show that the results of the regression are pasted directly into the spreadsheet. Notice that the coefficient of determination, R^{2}, is very close to 1. This might suggest that the choice of doing a cubic regression was a good one.
A cubic regression can be done with a minimum of four points. Under this scenario, TINspire finds a thirddegree polynomial fit by solving a system of four equations determined by using the x– and yvalues of the four points. With five or more points, TINspire performs a cubic regression.