PharmPK Discussion - Satherthwaite df in BE studies

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On 12 Feb 2004 at 04:26:35, Priti Pandey (priti_pandey.-at-.yahoo.com) sent the message

Dear Group,
  I would like to know difference between satterthwaite degree of
freedom and residual df. Why satherthwaite df is used for
Bioequivalence study analysis.
  One more query:What can be possible reasons of nve variance
components for PK parameter?
  Comments on this are welcome from the group.
  Thanks & regards,
Priti Pandey
Aurobindo Pharma Ltd.,
India

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On 12 Feb 2004 at 07:37:25, "Bonate, Peter" (pbonate.aaa.ilexonc.com) sent the message


Satterthwaite's degrees of freedom relates to estimating the degrees of
freedom in the numerator of an F-test for linear mixed effect models.
The residual degrees of freedom has to do with the denominator of the
F-test.  They are two different things.  Unless you have repeated
measures BE data, you don't need to worry about this.  But if you do,
then only when the data is balanced is the default numerator degrees of
freedom in SAS valid.  This is the containment method.  But if the data
are unbalanced you need to estimate the degrees of freedom based on the
data, which is what Satterthwaite's approximation does.
Hope this helps,
Pete Bonate

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