RE: [External] Re: RE: Stepwise covariate modeling
Thank you everyone for taking time out of your busy schedule to reply to my
question. I think all points were excellent. Gives me more to think about how
to proceed from here and make more informed decision about my model.
Regards,
Sumeet
Quoted reply history
-----Original Message-----
From: Leonid Gibiansky <[email protected]>
Sent: Tuesday, October 29, 2019 10:36 AM
To: Luann Phillips <[email protected]>; Singla, Sumeet K
<[email protected]>; [email protected]
Subject: [External] Re: [NMusers] RE: Stepwise covariate modeling
I think we are making it more difficult than needed, especially for the people
who just started using the NLME. It does not hurt to include statistically
significant covariate in the model even if the actual effect is small and does
no manifest itself on the standard diagnostic plots.
It make sense to check whether there is an error in the model code.
Plots of random effects versus covariates of interest should help to see
whether covariate model changed the individual random effects. If not (that is,
random effects of the model with and without covariate effect are numerically
identical) then the coding is wrong and should be checked.
Thanks
Leonid
On 10/29/2019 11:00 AM, Luann Phillips wrote:
> Hi,
>
> If _all_ of the individual predictions are the same for the model with
> the covariate and without the covariate, then it sounds like the
> original model is at a local minimum instead of a global minimum.
>
> Best regards,
>
> Luann
>
> *From:* [email protected] <[email protected]>
> *On Behalf Of *Singla, Sumeet K
> *Sent:* Tuesday, October 29, 2019 10:00 AM
> *To:* [email protected]
> *Subject:* [NMusers] Stepwise covariate modeling
>
> Hi!
>
> I am performing stepwise covariate modeling using PsN feature in Pirana.
> I am getting some covariates which are statistically reducing OFV
> significantly, however, when I include those covariates in the PK
> model, the results I am getting are exactly similar to what I am
> getting in my base model, i.e. there is no difference in individual
> predictions or pop predictions or any other diagnostic plots. So, does
> that mean I should move forward WITHOUT including those covariates as
> they don't seem to be explaining inter-individual variability despite
> scm telling me that they are statistically significant?
>
> Regards,
>
> *Sumeet K. Singla*
>
> *Ph.D. Candidate*
>
> *Division of Pharmaceutics and Translational Therapeutics*
>
> *College of Pharmacy | University of Iowa*
>
> *Iowa City, Iowa*
>
> *[email protected] <mailto:[email protected]>*
>
> *518.577.5881*
>