Cubic Regression

The cubic regression option finds the equation of the form y = ax3 + bx2 + cx + d that best fits a set of data. First, enter the data.

The data shown here are the points {(2,11.4), (3,17), (5,27.3), (7,36.1), (11,47.7), (13,49.9)}.

Press to view the statistics calculation options.

Press for regressions, then to select cubic.

Therefore, the best-fit cubic equation for this data is approximately y = -.00698x3 - .0859x2 + 6.17x - 5.67.

Note: The resulting cubic equation is an exact fit if four noncollinear, nonparabolic data points are entered. The correlation coefficient r is not calculated. If an error message occurs, make sure the data was entered correctly or press to view the setup.

Use , , and the menu keys to select List1 for 2Var XList, List2 for 2Var YList, and 1 for 2Var Freq.