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R: st: qladder


From   "Carlo Lazzaro" <carlo.lazzaro@tin.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   R: st: qladder
Date   Thu, 22 Sep 2011 15:00:57 +0200

Dear Ozgur,
I do not understand your concern.
If the -ovtest- does not reject the null hypothesis of no omitted variables,
your regression model has no misspecification problems (ie, all the relevant
explanatory variables are included in the RHS).

 
Kindest Regards,
Carlo

-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Ozgur Ozdemir
Inviato: giovedì 22 settembre 2011 13.57
A: Stata
Oggetto: RE: st: qladder



Thanks Nic,
you are right, in my case, residuals I think should be normally distributed
and i am happy with it but when I run the ovtest, it does not reject the
null hypothesis, that means, something is wrong with the transformations or
interactions within the model, not sure if i really need to pass the ovtest.
I did not see lots of papers reported ovtest results anyway.





kind regards
Ozgur 


----------------------------------------
> Date: Thu, 22 Sep 2011 12:52:31 +0100
> Subject: Re: st: qladder
> From: njcoxstata@gmail.com
> To: statalist@hsphsun2.harvard.edu
>
> I don't think I can suggest a complete list for you. You need to look
> at good publications in your field and talk to your
> advisors/supervisors/committee about what is expected. The idea of a
> link function is perhaps best covered in books on generalised linear
> models which, to be frank, are from what you say likely to be a tough
> read for you.
>
> That said, the purpose of -qladder- is to suggest transformations that
> make data more nearly normal. However, it is not an assumption of
> regression that data are normally distributed. Consider x = 1(1)10, y
> = 2 + 3x. Here regression makes perfect sense and it is not a problem
> that neither y nor x is normally distributed.
>
> Nick
>
> On Thu, Sep 22, 2011 at 12:42 PM, Ozgur Ozdemir
> <ozdemirozgur@hotmail.com> wrote:
> >
> >
> > Hi Nick,
> > that is great, thanks, what kind of link functions? meanwhile, I am very
new to Stata and just collected my data for my phd however still struggling
with regression analysis. it seems, it will be difficult than what I
expected. How can i find a complete list of activities to be done during a
regression / step by step journey ? it seems,  i am finding something new
everyday. thanks in advance.
> >
> >
> >
> >
> >
> >
> >
> > kind regards
> > Ozgur Ozdemir
> > T: +44 (0) 75 0332 9865
> > E: ozdemirozgur@hotmail.com<mailto:ozdemirozgur@hotmail.com>
> > Skype : ozgurozdemir2005
> >
> >
> > ----------------------------------------
> >> Date: Thu, 22 Sep 2011 12:38:44 +0100
> >> Subject: Re: st: qladder
> >> From: njcoxstata@gmail.com
> >> To: statalist@hsphsun2.harvard.edu
> >>
> >> It's enough that some are real zeros for the transformations concerned
> >> to be invalid. That doesn't rule out using link functions that indulge
> >> zeros.
> >>
> >> Nick
> >>
> >> On Thu, Sep 22, 2011 at 12:35 PM, Ozgur Ozdemir
> >> <ozdemirozgur@hotmail.com> wrote:
> >> >
> >> > Hi Nic,
> >> > It seems you are right, i have too many zeros but some of them are
real zeros, and some of them are missing values. i am not sure how I can
handle it.
> >> >
> >> >
> >> >
> >> >
> >> >> From: njcoxstata@gmail.com
> >> >> To: statalist@hsphsun2.harvard.edu
> >> >>
> >> >> The implication is that you have zeros in your data so that the
> >> >> transformations not plotted are not computable for all values. It is
> >> >> thus not clear that you are missing anything that could be useful.
> >> >>
> >> >> Nick
> >> >>
> >> >> On Thu, Sep 22, 2011 at 12:18 PM, Ozgur Ozdemir
> >> >> <ozdemirozgur@hotmail.com> wrote:
> >> >>
> >> >> > when I use the qladder command, it does show only four graphs
including cubic, square, identity and square root.   but does not show i.e
inverse, 1/square and some others. Is there any way that I can get others
graphed?
> >> >> >
>
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