Keith:

Thanks for sending the data.

I got an intercept of (8.9572) and slope of (-0.000043176) exactly like
you got.. I also got the same correlation coefficient.

To make sure that these results were valid, I used both the Excel Chart
liner trendline as well as Excel Intercept and Slope functions. Both methods
returned the exact same values.

I next used the formula Y = 8.9572 - 0.000043176* X to forecast your Y value
for an X of 169,200. I got 1.65, which plots right on the regression
trendline and is consistent with what you expect.

I am not sure how you got the 2.19. Can you double check the formula you
used to forecast Y.

As far as I can tell, your regression is working fine.


....Kelly




"Keith" wrote in message
...
Kelly,

The linear equation that Excel produces for the following data set is:

y = -4E-05x + 8.9573

with an R^2 of:

0.5539

X-Axis (Square Foot) & Y-Axis (Trip Rate)

128993 5.03
135197 2.94
129000 2.88
90255 5.30
135197 3.89
130316 4.31
129044 3.76
135197 4.25
135197 2.91
120059 5.01
164558 1.26
178207 1.13
105700 2.60
164775 1.41
164775 1.84
168044 2.36
123173 1.46
165129 1.10
163900 1.96
165030 2.20
163268 1.41
167400 1.69
139325 3.80
163704 2.43
163268 1.42
160680 1.75
130019 2.52

If I use the trendline that is plotted for the above data for 169200
square
feet I would expect a trip rate of approximately 1.6 to 1.8 however the
equation for that same line gives me a trip rate of 2.19.

Thanks Kelly

Keith





"Kelly O'Day" wrote:

Keith

I can't reproduce your results without some data. Can you copy paste the
X &
Y values?




"Keith" wrote in message
...
I have a scatter-point chart and I have been able to plot the linear
trendline through those scatter points. I then formatted the linear
trendline and got the equation for the line.

However, I noticed that the y-intercept (7.9...) of the actual line
that
was
graphed by Excel is not the same as the y-intercept (8.9573) for the
equation
that Excel derived from the graphed line. The actual Excel graphed line
and
the line the equation appear to be parallel to each other. As a
result,
entering data into the equation supposedly derived from the graphed
line
will
not result in the line that was graphed by Excel.

Thank you in advance for your help