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

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

posted by d_labes – Berlin, Germany, 2010-04-22 13:43 (5111 d 23:15 ago) – Posting: # 5183
Views: 59,282

Dear all, especially dear bears,

since I'm very interested in using R for evaluation of BE studies I had a closer look at the bear code for parallel group studies (code inspection as part of validation :-D

).

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. 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.

Nevertheless the lme() call produces a result.
Try it out in bear.

If I follow the strange and crude EMA suggestion and use all effects as fixed
lmModel <- lm(lnAUC0t ~ drug + subj, data=TotalData)
with the bear built-in dataset for parallel groups I get the anticipated result:


>summary(lmModel)

Call:

lm(formula = lnAUC0t ~ drug + subj, data = TotalData)



Residuals:

ALL 20 residuals are 0: no residual degrees of freedom! (over-specified!)



Coefficients: (1 not defined because of singularities)

            Estimate Std. Error t value Pr(>|t|)

(Intercept)   7.3199         NA      NA       NA

drug2        -0.0622         NA      NA       NA

subj2        -0.5366         NA      NA       NA

[...]


>anova(lmModel)

Analysis of Variance Table



Response: lnAUC0t

          Df  Sum Sq  Mean Sq F value Pr(>F)

drug       1 0.00127 0.001270               

subj      18 1.17959 0.065533               

Residuals  0 0.00000

BTW: I would go for a parallel groups study with exactly 2 groups with the 'simple' t-test (Welch variant as described by Helmut long ago) :cool:

.
Is anybody out there who knows a generalization of the Welch test to more than 2 groups? Any hint would be very appreciated!
Or could we use pairwise Welch t-tests for that?

—
Regards,

Detlew

Complete thread:

Parallel bears meeting at random in infinityd_labes 2010-04-22 11:43 [🇷 for BE/BA]
- Parallel bears meeting at random in infinity ElMaestro 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