Logarithmic Regression

The logarithmic regression option finds the equation of a logarithmic equation of the form y = a + b ln x that best fits a set of data. First, press to enter the data . The values of x must, of course, be greater than zero.

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 logarithmic equation for this data is approximately y = - 5.45 + 21.5 ln 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.