The quartic regression option finds the equation of a cubic equation of the form y = ax

Press and use to select CALC.

Press .

Therefore, the best-fit quartic equation for this data is approximately y = -0.69x

Press to view the regression equation and press . The equation is now entered in . Press . The data points can also be viewed. Access STAT PLOTS by pressing to turn the plots on. Press .

The TI-83 does not calculate the correlation coefficient r but does
calculate the coefficient of determination r^{2}. Press
to see it.

The value here of .99898 indicates a very good fit.