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From |
K Jensen <k.x.jensen@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Question about interactions |

Date |
Mon, 4 Mar 2013 16:30:03 +0000 |

Sorry to try your patience but can I test my understanding here? The results for 1-2 (say) are calculated from the main effect betas for variable1=1 and variable2=2? Thankyou Karin On 4 March 2013 15:37, Maarten Buis <maartenlbuis@gmail.com> wrote: > 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/ * * 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:*David Hoaglin <dchoaglin@gmail.com>

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

**Re: st: Question about interactions***From:*Maarten Buis <maartenlbuis@gmail.com>

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