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, enter
the data . Press .
to select CALC.
Therefore, the best-fit quadratic equation for this data is approximately
y = 3.09x2 - 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
to select EQ.
to view the regression equation and press .
The equation is now entered in .
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 r2. The value of
.995 indicates a very good fit.