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Re: st: Predict Command


From   anju parthan <aparthan@yahoo.com>
To   statalist@hsphsun2.harvard.edu, Jhilbe@aol.com
Subject   Re: st: Predict Command
Date   Thu, 10 Mar 2005 08:43:53 -0800 (PST)

Hi Jhile 

Thanks for the cautionary advice. 
When I run Poisson and then run the model again with
significant predictors, I get similar results. All the
variables are significant.

However, when I run nbreg, and then run the nbreg
model again with significant predictors, I dont get
the same results,some of the variables are not
significant anymore. So I am not sure how to use the
predict command to include only the significant
predictors. 

Also, when I run the predict command with nooffset
option after nbreg, the estimated values are between 0
and 1.  The dependent variable in the model is
absenteeism days and I adjusted for the exposure
period using exposure () option. 

My question is why are the values between 0 and 1?
What does it mean?

Am I missing something trivial here? Any thoughts?

Regards
Anju


--- Jhilbe@aol.com wrote:
> If you re-run the poisson model  using only
> predictors that appeared 
> significant in the larger model, you may  find that
> the previously significant 
> predictors are now not all significant. You  must
> check. Simply rerun the model using 
> only those predictors that were  significant and
> check to see if that still 
> remain the case. If it does, then  type -predict mu,
> mu- to get the predicted 
> counts, if that is what you want.  However, I myself
> double check predictors, 
> especially ones that have p-values  close to .05,
> with the likelihood ratio 
> test. The latter test is more reliable  than Z-, t-,
> or Wald tests. 
> 
> Joe  Hilbe
>
=========================================================
> Hi  All
> 
> I have a question on predict command. 
> 
> If I run a poisson  regression such as
> 
> poisson absdays male black hispanic 
> bluecollarworkers
> nohealthinsurance backpain comorbidconditions
> 
> where  all the independent variables are dummy
> variables. 
> 
> absdays=constant +  b1*male + b2*black + b3*hispanic
> +
> b4*bluecollarworkers +  b5*nohealthinsurance +
> b6*backpain + b7*comorbidconditions 
> 
> If from  the output only black, backpain, and
> comorbidconditions were statistically  significant,
> can
> I run the predict command to obtain
> the predicted number  of absdays using only the
> significant variables?
> 
> In otherwords can I  get the predicted absdays as
> 
> constant + b2*black + b6*backpain  +
> b7*comorbidconditions 
> 
> I know one option is to use the generate  command
> but I
> would like to know if we can do this using predict
> command  too. 
> 
> Thank you for your  time.
> 
> Regards
> Anju
> 
>
____________________________________________________________
> 
> Anju  Parthan, 
> Doctoral Candidate, 
> The University of Texas at Austin,  PHAR-PHARMACY
> ADMIN 
> 1 UNIVERSITY STATION A 1930, AUSTIN, TX-78712 
> Tel:  (512) 459-4942; Fax: (512) 471-8762
> 
> 
> 
> 
> 
> 
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____________________________________________________________
 
Anju Parthan, 
Doctoral Candidate, 
The University of Texas at Austin, PHAR-PHARMACY ADMIN 
1 UNIVERSITY STATION A 1930, AUSTIN, TX-78712 
Tel: (512) 459-4942; Fax: (512) 471-8762



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