## Quartic Regression

The quartic regression option finds the equation of a cubic equation of
the form y = ax^{4} + bx^{3} + cx^{2} + 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 = 0.005x^{4} + 0.013x^{3} - 0.44x^{2} - 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, r^{2}.