Exponential Regression

The exponential regression option finds the equation of an exponential equation of the form y = abx that best fits a set of data. First, press to enter the data . The values of 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 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 exponential equation for this data is approximately y = 11.78(1.133)x.

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.