This is not a numerically challenging calculation, so LINEST in Excel 2000
agrees with the chart trendline to 15 figures.

I do wish that MS would stop digging this hole deeper.

Jerry

"Jon Peltier" wrote:

The secret was in the OP's first line:

I have the home and student 2007 version.

Microsoft has "improved" their treatment of tiny rounding errors by
arbitrarily assuming certain small values are really supposed to be zero.
The ignored values are less then or around 1E-15, which corresponds to the
missing values in my testing (see my other post). This has messed up the
trendline regression formula, which used to be considered the best in the
business.

LINEST calculates the regression coefficients properly, at least in 2003 and
2007 (I didn't bother to test prior to this).

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
http://PeltierTech.com