Re: PSPP linear regression (reference category).

[Alan Mead]

If I understand your question, you're asking which is is the category against which each other dummy-coded category is compared? 

You select it when you dummy code.  When you have K categories, you create K-1 dummy variables and one group has a zero on all K-1 dummy variables.  That group is the reference group.

Think about it... the model for that group is missing the dummy coded variable and each of the remaining K-1 variables each have a regression coefficient that compares them to the reference group.

-Alan

On 9/29/2016 9:13 AM, Jack Drew wrote:

I use PSPP (current version 0.10.2) to generate linear regression models.  But, after checking the manual and help archive, I'm still having difficulty understanding how PSPP treats the reference categories for dummy variables, and if/how/what PSPP options let you set the reference.

Please could someone be kind enough to explain this feature in PSPP.

Thank you.  Jack

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Jack Drew

Senior Institutional Research Analyst

Office of Institutional Research

Mott Community College

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