Back to the Top
Is anyone in the group familiar with whether or not data for BE/BA
type studies should be ln-transformed prior to outlier analysis. I am
using Grubb's test which is based on the Z ratio and depending on
whether the data is transformed or not, there is a slight variation
in the results.
Thanks in advance.
Nav Coelho, M.Sc.
Biostatistician, Pharmacokinetics and Statistics
Biovail Contract Research
Back to the Top
>Is anyone in the group familiar with whether or not data for BE/BA
>type studies should be ln-transformed prior to outlier analysis.
1. yes, and 2. maybe ;-)
>I am using Grubb's test which is based on the Z ratio and depending
>on whether the data is transformed or not, there is a slight
>variation in the results.
What 'exactly' are you testing right now?
Since you are interested in doing the final analysis in the log-scale
you may test the individual ratios of untransformed responses (or
differences of logs).
Data mining does not make sence in a confirmatory trial (e.g.,
trying different statistical tests or playing around with
What variant of Grubb's test are you using - the one detecting
1 outlier or the one detecting 2 outliers?
Anyway in BE analyses we are not interested in the individual
BE-ratios - only reminds me on FDA's 75/75-rule ;-)
If you are interested whether your statistical assumptions for
ANOVA are valid, you should primarily look on the intra-subjects
Shapiro-Wilk for normality and for outliers maybe Hund's test, or
Tukey's sum-difference plot, or the Mahalanobis distance, or...)
Consultancy Services for Bioequivalence and Bioavailability Studies
tel/fax +43 1 2311746
Bioequivalence/Bioavailability Forum at http://forum.bebac.at
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (firstname.lastname@example.org)