Cubic Regression
The cubic regression option finds the equation of
the form y = ax3 + bx2 + cx + d that best fits a set of data.
First, enter the data.
The data shown here are 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 
for regressions, then
to select cubic.
Therefore, the best-fit cubic equation for this data is approximately
y = -.00698x3 - .0859x2 + 6.17x - 5.67.
Note:
The resulting cubic equation is an exact fit if four noncollinear, nonparabolic data points
are entered. The correlation coefficient r is not calculated. If an error message occurs, make
sure the data was entered correctly or press
to view the setup.
Use 
, 
,
and the menu keys to select List1 for 2Var XList,
List2 for 2Var YList,
and 1 for 2Var Freq.