## 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, enter
the data . Press .

Press
and use
to select CALC.

Press
and .

Therefore, the best-fit quadratic equation for this data is approximately
y = 3.09x^{2} - 5.25x + 4.33. The TI-83 stores the regression equation.
The equation can be graphed and is transfered to
without typing the equation as follows. Press
and use
to select EQ.

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 .

**Note:** The resulting quadratic equation is an exact fit if three noncollinear
data points are entered.
The TI-83 does not calculate the correlation coefficient r but does
calculate the coefficient of determination r^{2}. The value of
.995 indicates a very good fit.