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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Question about interactions |

Date |
Mon, 4 Mar 2013 16:37:30 +0100 |

On Mon, Mar 4, 2013 at 3:48 PM, K Jensen wrote: > I am fitting two four-point scales as predictors in a logistic > regression and am interested in looking at the interaction between the > two. > > If I fit variable1##variable2 I get odds ratios for the following: > variable1 > 2 > 3 > 4 > variable2 > 2 > 3 > 4 > variable1# > variable2 > 2 2 > 2 3 > 2 4 > 3 2 > 3 3 > 3 4 > 4 2 > 4 3 > 4 4 > > I obviously don't understand this because it doesn't include cells > 1-2, 1-3, 1-4, 2-1, 3-1 or 4-1. Can someone explain this? For both variables the category 1 is the reference category and is thus, together with its interaction terms, excluded. More on this, and alternatives, can be seen here: M.L. Buis (2012) "Stata tip 106: With or without reference", The Stata Journal, 12(1), pp. 162-164. <http://www.maartenbuis.nl/publications/ref_cat.html>. -- Maarten --------------------------------- Maarten L. Buis WZB Reichpietschufer 50 10785 Berlin Germany http://www.maartenbuis.nl --------------------------------- * * 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/

**Follow-Ups**:**Re: st: Question about interactions***From:*K Jensen <k.x.jensen@gmail.com>

**References**:**st: Question about interactions***From:*K Jensen <k.x.jensen@gmail.com>

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