Bioequivalence and Bioavailability Forum

FDA group model in R [Two-Stage / GS Designs]

posted by ElMaestro  – Denmark, 2016-10-17 20:58 (3170 d 00:52 ago) – Posting: # 16732
Views: 39,684

Hi VStus,

❝ Maybe lm() sometimes doing exactly the same as PROC GLM?

I actually lost a bit track of this discussion and I am not exactly sure what the comparisons try to achieve?!?
However, lm() and PROC GLM are related but not the same and they do not necessarily achieve exactly the same result. I am very sure that their behavour corresponds to the specification, and I have good reason to think their output is correct cf. those specifications. I do not know how SAS handles crosses and interactions, but I know that anova on lm() in R puts main effects first.
Drop1 is a good example of a source of differences in terms of results. Drop1 and type III is implemented differently in R and SAS. You can argue both are right, certainly, even though they are not identical results. Drop1 in R involves single term deletions which is how type III is defined, but that may give a zero SS (or SS decrease) for sequence. In SAS type III involves deletion of more than just single terms for between-factors in our BE studies so that sequence is not a zero SS effect.

So, before you start comparing lm() (with or without anova or drop1) and SAS, perhaps you can formulate with your own words what you want calculated and how, when there is room for interpretation such as is the case with type I/III and lm()/drop1 versus PROC GLM.

Complete thread:

• Potvin C in the EU Helmut 2013-04-16 17:40 
  • Potvin C in the EU ElMaestro 2013-04-17 02:31
    • Potvin C in the EU Helmut 2013-04-17 12:23
      • 2 Groups model FDA d_labes 2013-04-17 13:10
        • 2 Groups model FDA Helmut 2013-04-17 16:37
          • Group effects obsolete? d_labes 2013-04-18 09:55
            • Group effects FDA/EMA Helmut 2013-04-19 14:34
              • Group effects FDA/EMA mittyri 2014-08-21 15:34
                • Group effects FDA/EMA ElMaestro 2014-08-21 17:31
                  • Group effects EMA mittyri 2014-10-01 11:25
                    • Group effects EMA ElMaestro 2014-10-01 11:31
                    • Group effects EMA Helmut 2014-10-01 13:24
                      • Group effects EMA VStus 2016-10-06 22:06
                        • Group effects EMA ElMaestro 2016-10-07 12:45
                          • Group effects EMA mittyri 2016-10-07 15:06
                            • Fixed effects model with Group term mittyri 2016-10-09 13:27
                              • Fixed effects model: changing the F, p values mittyri 2016-10-10 18:33
                                • Fixed effects model: changing the F, p values ElMaestro 2016-10-10 20:10
                                  • Fixed effects model: changing the F, p values Helmut 2016-10-11 00:17
                                  • Holy War of type III d_labes 2016-10-11 13:17
                                    • Significance of Group effect in Russia: why the type III is so 'important' mittyri 2016-10-11 15:07
                                • Fixed effects model: changing the F, p values zizou 2016-10-11 01:06
                                  • FDA group model in R mittyri 2016-10-11 13:43
                                    • FDA group model in R ElMaestro 2016-10-12 01:07
                                    • FDA group model in R VStus 2016-10-17 15:32
                                      • FDA group model in RElMaestro 2016-10-17 18:58
                                        • FDA group model in R VStus 2016-10-20 13:57
                              • Fixed effects model with Group term VStus 2016-10-20 13:54
                  • Group effects FDA/EMA zizou 2016-12-31 02:54
                    • Group effects FDA/EMA Helmut 2017-06-03 14:57
          • 2 Groups model FDA hiren379 2013-08-22 14:32
            • Homework Helmut 2013-08-23 11:53