Bioequivalence and Bioavailability Forum • Negative variance component

Negative variance component [Software]

posted by ElMaestro – Denmark, 2014-01-31 09:20 (4099 d 12:54 ago) – Posting: # 12300
Views: 27,818

Hi,

❝ if(Hypothesis = 'Sequence*Subject', 100*sqrt(exp((MS-MSerror)/2)-1), ''), in my data MS is smaller than MSerror hence the resultant number before taking last step squareroot becomes negative.

❝ Is it true that in the case the intersubject CV is considered nonestimable? Or is there other way to calculate this out?

I think PHX is in mixed mode here. I'd switch to an all-fixed model. The results is the same as long as we talk standard 2,2,2-BE. If you really want to apply a mixed model for the result, then you can probably first do the all-fixed trick to get estimates of effects and between + within variances, then use the results coming from the all-fixed analysis as starter guess for the optimizer in the mixed model. That also puts less stress on the optimiser so your risk of getting trouble with the optimizer worker's union is low :-D

I am not a PHX/winnonlin user so I do not know the syntax for this approach.

Finally, without knowing anything about PHX/winnonlin, how about trying Subject everywhere rather than Sequence*Subject or Subject*Sequence?

—
Pass or fail!
ElMaestro

Complete thread:

How to calculate intersubject variability in PHX WinNonlin zan 2014-01-29 23:58 [Software]
- Negative variance component Helmut 2014-01-30 01:16
  - Negative variance component zan 2014-01-30 18:11
  - Negative variance component zan 2014-01-31 00:16
    - Negative variance componentElMaestro 2014-01-31 08:20
    - Negative variance component yjlee168 2014-01-31 10:26
      - Example data set Helmut 2014-02-01 16:03
        
        Example data set yjlee168 2014-02-01 17:40
        
        PHX build 6.3.0.395 / 6.4.0.511 Helmut 2014-02-02 02:04
        
        PHX build 6.3.0.395 / 6.4.0.511 yjlee168 2014-02-02 07:54
    - Negative variance component ElMaestro 2014-02-01 16:31
      - Negative variance component yjlee168 2014-02-01 17:47
        
        Just thinking loud ElMaestro 2014-02-01 19:02
        
        All models are wrong… Helmut 2014-02-02 02:31
        
        another book for linear model yjlee168 2014-02-02 08:07
      - References Helmut 2014-02-02 02:19
        
        References ElMaestro 2014-02-02 09:56
    - Negative variance component – Chow/Liu d_labes 2014-02-03 09:02
      - Negative variance component – Chow/Liu ElMaestro 2014-02-03 10:22
        
        Variance components – Proc mixed d_labes 2014-02-03 11:58
        
        Variance components – Proc mixed ElMaestro 2014-02-03 12:58
        
        Variance components – Proc mixed 90% CIs d_labes 2014-02-03 13:16
        Variance components – Proc mixed Helmut 2014-02-03 14:14
        
        FDA code for non-replicate crossover? d_labes 2014-02-03 15:54
        
        Proc GLM rulez Helmut 2014-02-03 16:16
        
        Variance components – Proc mixed yjlee168 2014-02-03 20:43
        
        NOBOUND Helmut 2014-02-03 22:08
      - lm() or lme() for 2x2x2 study design? yjlee168 2014-02-03 20:22
        
        lm() or lme() for 2x2x2 study design? ElMaestro 2014-02-03 22:11
        
        lm() or lme() for 2x2x2 study design? yjlee168 2014-02-04 13:09
        
        bear for 2x2x2 study with negative variance components yjlee168 2014-02-05 19:12