How do I compare two levels of IV in a multiple regression?

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Vic100
Posts: 2
Joined: Thu Dec 11, 2014 9:55 am

How do I compare two levels of IV in a multiple regression?

Postby Vic100 » Thu Dec 11, 2014 10:04 am

Hi all,

I'm very new to SPSS (using version 21) and statistics in general and am a bit stuck!

I need to do a multiple regression (I'm looking at how attitudes predict behaviour). I have one DV with continuous data and two IVs, also both with continuous data, but one IV has two nominal levels (these are two age groups, so I want to compare attitudes and behaviour for each age group).

I don't know whether I need to run two separate regressions for each level or combine them in one. Combining them makes more sense but I have no idea how to do this. If I ran two separate regressions then would I have to recheck parametric assumptions for each set of data?

I've been trying to figure this out for two days and am just not getting anywhere. Any help will be greatly appreciated.

Many thanks,
Vic
GerineL
Moderator
Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: How do I compare two levels of IV in a multiple regressi

Postby GerineL » Thu Dec 11, 2014 9:36 pm

You can include an interaction in your regression.
There are a lot of case-studies online.
In your case, it might be comparable to an analysis with gender (also 2 levels / nominal), so you could try to look at that to see if you can apply it to your own data.
Vic100
Posts: 2
Joined: Thu Dec 11, 2014 9:55 am

Re: How do I compare two levels of IV in a multiple regressi

Postby Vic100 » Fri Dec 12, 2014 10:46 pm

Thanks very much for the tips. I'll take a look.

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