## Power Regression

The power regression option finds the equation of an equation of
the form y = ax^{b} that best fits a set of data.
First, press
to
enter the data .
The values of x and y must be greater than zero. (This is because the method for determining
the values of a and b in the regression equation is a least-squares fit on the
values for ln x and ln y.)

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 power equation for this data is approximately y = 7.01x^{.8}.
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 TI-85 calculates the correlation coefficient, r, as corr.