Bioequivalence and Bioavailability Forum • Parallel bears meeting at random in infinity

Parallel bears meeting at random in infinity [🇷 for BE/BA]

posted by ElMaestro – Denmark, 2010-04-22 14:53 (5484 d 01:58 ago) – Posting: # 5184
Views: 58,241

Ahoy d_labes!

❝ If I got it right the code used is (f.i. AUC log-transformed):

❝ lme(lnAUC0t ~ drug, random=~1|subj, data=TotalData, method="REML" )

❝ I am wondering where this code comes from, what this code does an why it works anyhow :ponder: .

❝ IMHO this model, one (fixed) effect for the treatment and one (random) effect for the subjects must be over-specified.

With REML, the likelihood is optimised on the covariance matrix V (=ZGZ^t+R). With "random=~1|subj" I think we do the most simple specification of V, as we put in sigma on the diagonal, and zeros elsewhere. Thus, subjects introduce a random effect (think sigma on the diagonal), nature of treatment not considered.

❝ We have only one value for a distinct subject treated with Test or Reference and thus we are not able to separate this uniquely into 2 effects, one part for treatment and one attributed to the subject.

In my opinion, and I could be wrong, with this specification of the model we are not trying to do exactly that through the proposed code. We are only saying that each subject is associated with a degree of variability which is described by a common sigma in V, regardless of the treatment given for any data point.

Best regards from the seven seas,
EM.

Correction: I mean sigma² on the diagonal.

—
Pass or fail!
ElMaestro

Complete thread:

Parallel bears meeting at random in infinity d_labes 2010-04-22 11:43
- Parallel bears meeting at random in infinityElMaestro 2010-04-22 12:53
  - Parallel groups in bear - CIs d_labes 2010-04-22 14:00
    - Parallel groups in bear - CIs ElMaestro 2010-04-22 21:47
      - Parallel groups in bear - CIs d_labes 2010-04-23 09:09
    - Parallel groups in bear - CIs yjlee168 2010-04-25 23:29
- Parallel bears meeting at random in infinity yjlee168 2010-04-22 23:09
  - Modelling Parallel bears d_labes 2010-04-23 09:12
    - Modelling Parallel bears yjlee168 2010-04-23 21:14
      - Validating vs. WinNonlin... Helmut 2010-04-24 00:28
        
        Validating vs. WinNonlin... yjlee168 2010-04-24 19:36
        Validating vs. WinNonlin... yjlee168 2010-04-26 00:09
        
        Validating vs. WinNonlin... Helmut 2010-04-26 01:29
        
        WNL in replicate BE yjlee168 2010-04-26 08:59
        
        WNL in replicate BE Helmut 2010-04-26 16:15
      - Modelling Parallel bears yjlee168 2010-04-25 19:34
        
        Modelling Parallel bears ElMaestro 2010-04-25 20:40
        Dataset Helmut 2010-04-25 22:38
        
        Dataset yjlee168 2010-04-25 22:44
        
        Dataset Helmut 2010-04-26 01:13
        
        Dataset yjlee168 2010-04-26 08:16
        
        NCA → Statistical analysis for parallel study Helmut 2010-04-26 13:12
        
        NCA → Statistical analysis for parallel study yjlee168 2010-04-26 18:43
        
        dilemma yjlee168 2010-04-26 08:41
        Equal variances d_labes 2010-04-26 09:04
        
        Equal variances yjlee168 2010-04-26 09:22
        
        GLM = Equal variances d_labes 2010-04-26 13:29
        
        GLM = Equal variances Helmut 2010-04-26 14:45
        
        I'm a believer d_labes 2010-04-26 15:58
        
        I'm a believer Helmut 2010-04-26 16:31
        
        Equal variances Helmut 2010-04-26 12:55
        
        gls() for unequal variances? d_labes 2010-04-26 16:36
        
        gls() for unequal variances? Helmut 2010-04-26 17:00
        Sims Helmut 2010-04-27 01:36
        
        Sandwich - Simsalabim d_labes 2010-04-28 10:58
        
        Sandwich - Simsalabim Helmut 2010-04-28 14:19
        parametrization of R function rlnorm martin 2010-05-02 18:22
        
        Mean of log-normal d_labes 2010-05-03 16:22
        parametrization of R function rlnorm ElMaestro 2013-07-26 21:42
        
        Martin‽ Helmut 2013-07-28 02:01