Quadratic Regression

The quadratic regression option finds the equation of a quadratic equation of the form y = ax2 + bx + c 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 quadratic equation for this data is approximately y = - 0.049x2 + 0.47x - 1.44.

Note: The resulting quadratic equation is an exact fit if three noncollinear data points are entered.

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