## Quadratic Regression

The quadratic regression option finds the equation of a quadratic equation of
the form y = ax^{2} + 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 = - 0.049x^{2} + 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, r^{2}.