SPSS GLM or Regression? When to use each

April 23rd, 2009 by

Regression models are just a subset of the General Linear Model, so you can use GLM procedures to run regressions.  It is what I usually use.

But in SPSS there are options available in the GLM and Regression procedures that aren’t available in the other.  How do you decide when to use GLM and when to use Regression?

GLM has these options that Regression doesn’t: (more…)

Dummy Coding in SPSS GLM–More on Fixed Factors, Covariates, and Reference Groups, Part 2

March 31st, 2009 by

Part 1 outlined one issue in deciding whether to put a categorical predictor variable into Fixed Factors or Covariates in SPSS GLM.  That issue dealt with how SPSS automatically creates dummy variables from any variable in Fixed Factors.

There is another key default to keep in mind. SPSS GLM will automatically create interactions between any and all variables you specify as Fixed Factors.

If you put 5 variables in Fixed Factors, you’ll get a lot of interactions. SPSS will automatically create all 2-way, 3-way, 4-way, and even a 5-way interaction among those 5 variables. (more…)

SPSS GLM: Choosing Fixed Factors and Covariates

December 30th, 2008 by

The beauty of the Univariate GLM procedure in SPSS is that it is so flexible.  You can use it to analyze regressions, ANOVAs, ANCOVAs with all sorts of interactions, dummy coding, etc.

The down side of this flexibility is it is often confusing what to put where and what it all means.

So here’s a quick breakdown.

The dependent variable I hope is pretty straightforward.  Put in your continuous dependent variable.

Fixed Factors are categorical independent variables.  It does not matter if the variable is (more…)