Re: st: or option for ologit does not work after mi stimate

["Sheena Sullivan" <sheena.sullivan@gmail.com>]

I had a similar problem to that posted earlier by Roland, except for time
ratios derived from an accelerated failure time model.  So, I wanted to
share it with the Statalist in case anyone else ran into the same problem
and to ask a question about the eform option.

Typically, to get time ratios I would type the following: 
streg Y X Z, dist(lnormal) frailty(gamma) sh(G) tr
Where the -tr- option produces the time ratio. 

If I use mi estimate, I can type the same thing:
mi estimate: streg Y X Z, dist(lnormal) frailty(gamma) sh(G) tr
But -tr- is ignored and only the coefficients are displayed.  

I followed the solution for Roland to type the option in the mi estimate
command, i.e:
mi estimate, tr: streg Y X Z, dist(lnormal) frailty(gamma) sh(G)
But the tr option is not allowed.  

If I instead use the eform option I do get my exponeniated coefficients:
mi estimate, eform: streg Y X Z, dist(lnormal) frailty(gamma) sh(G)

But I wanted to ask the Stata community whether there are any issues I
should know about when using this option for accelerated failure time
models?  As far as I understand, the time ratios are just exponentiated
coefficients, so I assume it should be okay.  Is the -tr- option not allowed
because it can be achieved with the eform option?  Or is it unwise to
exponentiate these coefficients and their corresponding confidence
intervals?


As an addendum, to get both coefficients and ratios, I saved the estimates,
which seemed to work
mi estimate, saving(mi_aft_ests.ster, replace) : streg streg Y X Z,
dist(lnormal) frailty(gamma) sh(G)
mi estimate using mi_aft_ests.ster, eform

Thanks
Sheena  


________________________________________
From
  roland andersson <rolandersson@gmail.com>
To
  statalist@hsphsun2.harvard.edu
Subject
  Re: st: or option for ologit does not work after mi stimate
Date
  Tue, 4 Jan 2011 16:31:18 +0100
________________________________________
Thank you Marten.
It works.

Roland Andersson

2011/1/3 Maarten buis <maartenbuis@yahoo.co.uk>:
> --- On Mon, 3/1/11, roland andersson wrote:
>> I want to have the odds ratio rather than the coefficients
>> after -mi estimate- but the -or- option does not work. The
>> two models
>> mi estimate: ologit dgn variables
>> mi estimate: ologit dgn variables, or
>>
>> I can of course calculate the ORs manually, but is this a
>> bug?
>
> It is not a bug. Commands like -mi estimate- work with the
> returned results (e.g. the matrices e(b) and e(V)) and these
> are not affected by the -or- option, so the results should
> not change. Instead you should tell -mi estimate- directly
> that you want the exponentiated results by specifying the
> -or- option within -mi estimate-:
>
> *------------------ begin example ---------------------
> webuse mheart1s20
> mi describe
> mi estimate, or: logit attack smokes age bmi hsgrad female
> *------------------- end example -----------------------
>
> Hope this helps,
> Maarten
>
> --------------------------
> Maarten L. Buis
> Institut fuer Soziologie
> Universitaet Tuebingen
> Wilhelmstrasse 36
> 72074 Tuebingen
> Germany
>
> http://www.maartenbuis.nl
> --------------------------



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