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 .

The data shown here is the points {(2,11.4) (3,17) (5,27.3) (7,36.1) (11,47.7) (13,49.9)}.

Press to view the statistics calculation options.

Press .

Therefore, the best-fit linear equation for this data is approximately y = -.23x2 + 7.13x - 2.11.

The regression equation can be automatically stored in the equation editor by pressing then typing the name of the equation, such as y1, and pressing .

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

The TI-85 does not calculate the correlation coefficient r.