Using Select cases and regression at the same time in SPSS

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maja
Posts: 4
Joined: Wed Aug 13, 2014 9:27 am

Using Select cases and regression at the same time in SPSS

Postby maja » Mon Nov 03, 2014 8:28 pm

Hello everyone,
I want to do a regression to estimate coefficients before and after a certain treatment happened, I used select cases: I first selected the data before treatment happened and I did a regression on this data. Afterwards I selected the data after treatment and I did the same regression on this data. Is this correct or do I have to add dummy variables with 0 when it is whithout treatment and 1 after the treatment took place and do the regression on the entire data? What is the difference?
GerineL
Moderator
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Joined: Tue Jun 10, 2008 4:50 pm

Re: Using Select cases and regression at the same time in SP

Postby GerineL » Tue Nov 04, 2014 9:39 am

You can do it as you said, but then you can't see if there is actually a difference in coefficients before and after treatment (i.e., if differences you find are significantly different).
maja
Posts: 4
Joined: Wed Aug 13, 2014 9:27 am

Re: Using Select cases and regression at the same time in SP

Postby maja » Wed Nov 05, 2014 11:46 am

GerineL wrote:You can do it as you said, but then you can't see if there is actually a difference in coefficients before and after treatment (i.e., if differences you find are significantly different).
But if I do it on my way, I have the estimated coefficients before and after the treatment. Is there a test to test if the coefficients are significantly different?
GerineL
Moderator
Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: Using Select cases and regression at the same time in SP

Postby GerineL » Wed Nov 05, 2014 12:19 pm

Not that I know of, but there might be. Please let me know if you find a way though :-)

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