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Re: st: Interpretation of regressionmodel of ln-transformed variable


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interpretation of regressionmodel of ln-transformed variable
Date   Wed, 5 Nov 2008 15:07:15 +0000 (GMT)

Sounds correct (though I can only certify the parts of the message in
English or Stata)

-- Maarten

--- roland andersson <rolandersson@gmail.com> wrote:

> Maarten
> 
> Det er jo glimrende o dejlig
> 
> Just to assure I have understood. In this model I keep age 10-19 and
> non-perforated appendicitis (the largest groups) as reference level
> so
> I do not bother with mean centering with age.
> 
> 
> lnLOS              exp(b)       Std. Err.      t        P>t
> [95% Conf. Interval]
> 
> lapscopy         1.015229   .0069404     2.21   0.027     1.001716   
> 1.028924
> _Iappdgn2_1    1.854565   .0133561    85.76   0.000     1.828571   
> 1.880929
> _Iappdgn2_3    1.172527   .0139403    13.39   0.000      1.14552   
> 1.200171
> _Ialderkat_0     1.113349   .0124712     9.59   0.000     1.089172   
> 1.138063
> _Ialderka~20    .9669727   .0081023    -4.01   0.000     .9512217   
> .9829846
> _Ialderka~30    1.013716   .0091096     1.52   0.130     .9960177    
> 1.03173
> _Ialderka~40    1.074382   .0115025     6.70   0.000     1.052072   
> 1.097165
> _Ialderka~50    1.181179   .0134386    14.64   0.000      1.15513   
> 1.207815
> _Ialderka~60    1.309059   .0192205    18.34   0.000     1.271924   
> 1.347279
> _Ialderka~70    1.685401   .0312085    28.19   0.000     1.625328   
> 1.747694
> _Ialderka~80    2.303874   .0611701    31.43   0.000     2.187045   
> 2.426943
> prepermalign    1.190686    .027653     7.51   0.000     1.137701    
> 1.24614
> precardios~s    1.024731   .0266026     0.94   0.347     .9738935   
> 1.078222
> preperlung~d    1.076669   .0182661     4.35   0.000     1.041456   
> 1.113073
> preperhype~i    1.024272   .0208447     1.18   0.239     .9842196   
> 1.065954
> preperhjar~t     1.293909   .0480737     6.94   0.000     1.203033   
> 1.391651
> prepernjur~t     1.050412   .0516992     1.00   0.318      .953814   
> 1.156792
> preperdiab~s    1.168423   .0287019     6.34   0.000     1.113499   
> 1.226055
> cons                1.858693   .0106446   108.24   0.000     1.837946
>   1.879675
> 
> And here I calculate the effect of laparoscopy
> 
> . nlcom exp((_b[cons]+ _b[lapscopy]) -  exp((_b[cons])))
> 
> _nl_1:  exp((_b[cons]+ _b[lapscopy]) - exp((_b[cons])))
> 
> 
> vtidln       Coef.   Std. Err.      t    P>t     [95% Conf. Interval]
> 
> _nl_1    .2941382   .0027509   106.92   0.000     .2887463   
> .2995302
> 
> ie open appendectomy in nonperforated patients age 10-19 have a
> geometric mean LOS of 1.86 (95% CI 1.83-1.88) days after adjustment
> for comorbidity and lapscopy patients have 0.29 (95% CI 0.28-0.30)
> days longer LOS.
> 
> Correct?
> 
> Greetings o stort tack
> 
> Roland Andersson


-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room N515

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


      
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