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.
Press 
.
Enter the columns to be used for the x and y entries, c1 and c2 in this case.
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-92 does not calculate the correlation coefficient r. It does calculate the coefficient
of determination.