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.