st: Chow test to test only slope coefficient and importance of dummy variable?

[<savinett@ucalgary.ca>]

Hi,

I am new to Stata and the Chow Test. I want to compare the slopes of two
sets of time series data using the chow test, however I am not interested
in any differences in the intercepts of these time series data.  I have
read the FAQs section on this and found this one: 
http://www.stata.com/support/faqs/statistics/chow-tests/ to be very
helpful.  I do, however, have two questions:

1.   Can I use the Chow Test to test that only the slopes are different
(not both the slope and intercepts)? I still want to include the intercept
in the model (i.e. not use the ?noconstant?). However, for the Chow Test I
would like it to reflect that if there is a significant difference between
the groups that this is due to a difference in their slopes (as I expect
that their intercepts will differ and am not interested this aspect).

2.  It is not clear to me why the in the example from the Chow Test FAQ
(link in the first paragraph) ?group2? (the dummy variable) is included in
the regression:
. regress price mpg weight mpg2 weight2 group2

If someone could please provide me with some insight that would be amazing.
Thank you very much in advance for your help with my questions!

Sarah



*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/