## 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 .

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.

To find the quadratic (P2Reg) polynomial of degree two regression option, press
.

Now, select quadratic regression. Press
.

.

Therefore, the best-fit quadratic equation for this data is approximately
y = -.23x^{2} + 7.13x - 2.11.

**Note:** The resulting quadratic equation is an exact fit if three non-collinear data points
are entered.
The TI-86 does not calculate the correlation coefficient r.