The exponential regression option finds the equation of an exponential
equation of the form y = abx that best fits a set of data. First,
the data . Press
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.) Press
to select CALC.
(The exponential regression option can also be obtained by using the
to select option A and pressing .)
Therefore, the best-fit exponential equation for this data is approximately
y = 2.80(0.84)x. The TI-82 calculates the correlation coefficient,
r. In this case, r is about -0.97. The value of r lies between -1 and 1,
inclusive. It is a measure of how well the regression equation fits the
data. A value of -1 or 1 indicates a perfect fit.
The TI-82 stores the regression equation. The equation can be graphed
and is transfered to
without typing the equation as follows. Press
to select EQ.
to view the regression equation and press .
The equation is now entered in .
The data points can also be viewed. Access STAT PLOTS by pressing
to turn the plots on. Press .
Note: The TI-82 calculates the correlation coefficient r.