jemelland -

The power and exponential trendline options are grayed out (not available)
in my Excel 2003. Why is this and how do I fix it? <

Here are some edited excerpts from my book "Data Analysis Using Microsoft
Excel: Updated for Office XP":

The power model creates a trendline using the equation
y = c * x^b.
Excel uses a log transformation of the original x and y data to determine
fitted values, so the values of both the dependent and explanatory variables
in your data set must be positive. If any y or x values are zero or
negative, the Power icon on the Add Trendline Type tab will be grayed out.
(As a workaround, you can add a constant to each y and x value.)

The exponential model creates a trendline using the equation
y = c * e^(b*x).
Excel uses a log transformation of the original y data to determine fitted
values, so the values of the dependent variable in your data set must be
positive. If any y values are zero or negative, the Exponential icon on the
Add Trendline Type tab will be grayed out. (As a workaround, you can add a
constant to each y value.)

- Mike
http://www.MikeMiddleton.com