Quartic Regression


The quartic regression option finds the equation of a cubic equation of the form y = ax4 + bx3 + cx2 + dx + e that best fits a set of data. First, press to enter the data .



Press to view the statistics calculation options.

Enter the columns to be used for the x and y entries, c1 and c2 in this case.



Press .



The regression equation can be automatically stored in the equation editor by selecting the Stor RegEQ.



Therefore, the best-fit quartic equation for this data is approximately y = 0.005x4 + 0.013x3 - 0.44x2 - 0.34x + 2.13.


Note: The resulting quartic equation is an exact fit if five noncollinear, nonparabolic, noncubic data points are entered.

The TI-89 does not calculate the correlation coefficient r. It does calculate the coefficient of determination, r2.