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Re: st: Ologit question
From
"Anat (Manes) Tchetchik" <[email protected]>
To
[email protected]
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 <[email protected]> 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
> ---------------------------------
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--
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: [email protected]
Phone 972-(0)8-6479735
Fax: 972-(0)8-6472920
Web: http://cmsprod.bgu.ac.il/Eng/som/hotelmanage/Staff/Academic/ChechikA.htm
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