Quartic Regression

The quartic regression option finds the equation of a fourth degree polynomial of the form

y = ax4 + bx3 + cx2 + dx + e

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)}.

To view the statistics calculation options press .

Press find the quartic regression optiion -- polynomial of degree four, P4Reg.

Select P4Reg, .

Run quartic regression by pressing . Scroll to the right to see all of the coefficients.

Therefore, the best-fit quartic equation for this data is approximately y = .00011x4 - .0104x3 - .0504x2 + 6.037x - 3.89. (Note the scientific notation for the first term.)

Note: The resulting quartic equation is an exact fit if five non-collinear, non-parabolic, non-cubic data points are entered.

The TI-86 does not calculate the correlation coefficient r.