Jerry,

I think I've figured out what your meant by "xy scatter"!
I modified my data table the following way and got the right results:

X Y
73 6.6
74
75
76
77
78 5.8
.... ...

Thanks for your help.

Jan M.



"Jerry W. Lewis" wrote:

> Use an "XY (Scatter)" chart.
>
> When you selected a "Line" chart, you (by definition) told Excel that your
> x-axis was categorical instead of numeric, and that what you provided for the
> x-axis was a set of category labels that may or may not have numeric values.
> Why Excel would offer to fit a trendline in that circumstance is a mystery to
> me, but when it does, it uses x-values of 1,2,3,... and correctly calculates
> the regression of y against those assumed x-values.
>
> Jerry
>
> "Jan M." wrote:
>
> > Hi,
> >
> > I created a bar chart in Excel from the following data:
> >
> > X Y
> > 73 6.6
> > 78 5.7
> > 86 4.8
> >
> > The SLOPE and the INTERCEPT functions returned -0.136 and 16.4448
> > respectively. The resulting equation is Y = -0.136X + 16.448 which seems good
> > enough to me.
> >
> > Then I added a linear trendline to the chart. Excel displayed the following
> > equation: Y = -0.9X + 7.5, R ^2 =1 which is way off (and it's not a rounding
> > problem)!!!
> >
> > The data seemed farly linear to me, how come Excel can't come up with the
> > right equation???
> >
> > Thanks
> >
> > Jan M.
> >
> >