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From |
"Anat (Manes) Tchetchik" <anatmanes@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Ologit question |

Date |
Wed, 31 Oct 2012 15:58:47 +0200 |

Thank you Maaraten, Running -test- yeilds : test ( 1) [tier_reversed]profit = 0 ( 2) [tier_reversed]oncology = 0 ( 3) [tier_reversed]cardiology = 0 ( 4) [tier_reversed]clinical_services = 0 ( 5) [tier_reversed]length_stay_tot = 0 ( 6) [tier_reversed]age = 0 ( 7) [tier_reversed]income = 0 ( 8) [tier_reversed]H_index = 0 ( 9) [tier_reversed]publications = 0 (10) [tier_reversed]doctors = 0 (11) [tier_reversed]revenue = 0 Constraint 11 dropped chi2( 10) = 24.65 Prob > chi2 = 0.0060 not sure I understand what it means and how it referes to the cuts Anat On Wed, Oct 31, 2012 at 3:46 PM, Maarten Buis <maartenlbuis@gmail.com> wrote: > On Wed, Oct 31, 2012 at 2:23 PM, Anat (Manes) Tchetchik wrote: >> I ran an Ologit and received the following cutoffs: >> >> Coef. Std. Err. [ 95% Conf. Interval] >> /cut1 | -1.798009 2.900799 -7.483471 3.887453 >> /cut2 | .7973023 2.793147 -4.677166 6.271771 >> /cut3 | 2.902347 2.794626 -2.57502 8.379713 >> which means that the cutoffs are not significantly different. > > You seem to perform this test by looking at whether the confidence > intervals overlap. This is not a correct way to perform such a test, > as that way you ignore the covariances in the sampling distribution of > these estimates. Instead you should use -test- if you want to perform > such a test. > >> Does it mean that the entire model is worthless? > > No, statistical tests do not represent a relevant tradeoff you need to > make when choosing a model. The tradeoff implicit in a statistical > test is all about the probability of rejecting a true null hypothesis > and the probability of not rejecting a false hypothesis. However, it > is by definition impossible for a model to be "true". A model is by > definition a simplification of reality, and a simplification is just > another word for "wrong in some useful way". So you want your model to > be wrong (simplify) in such a way that the results become manageable > for a human brain to process, but at the same time you don't want your > model to be too wrong so that it deviates too much from your raw > observations. So selecting a model and doing a statistical test are > fundamentally different beasts working with very different logics, > which means that a statistical test just cannot inform you about which > model is "right" or "wrong". > > -- 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/ -- Anat Tchetchik, PhD Department of Hotel and Tourism Management Guilford Glazer Faculty of Business and Management Ben-Gurion University of the Negev P.O.Box: 653 Beer-Sheva, Israel, 84105 E-mail: anat@som.bgu.ac.il Phone 972-(0)8-6479735 Fax: 972-(0)8-6472920 Web: http://cmsprod.bgu.ac.il/Eng/som/hotelmanage/Staff/Academic/ChechikA.htm * * 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: Ologit question***From:*Maarten Buis <maartenlbuis@gmail.com>

**References**:**st: Ologit question***From:*"Anat (Manes) Tchetchik" <anatmanes@gmail.com>

**Re: st: Ologit question***From:*Maarten Buis <maartenlbuis@gmail.com>

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