Example [Regulatives / Guidelines]

posted by Helmut Homepage – Vienna, Austria, 2017-05-02 14:35 (2604 d 02:45 ago) – Posting: # 17291
Views: 30,690

Hi ElMaestro,

❝ Could you tell how you got your F-test denominator? I am sure you are right, but I don't know where it came from. For an interaction of a between- and within-factor I think the rule of thumb (which is also a wee bit hard to define :-D) is to test against the within, which in this case would be the model residual.


Yep. Below an example of model 1 in Phoenix/WinNonlin. Two groups (n=24 each), all effects fixed.

Partial Sum of Squares
            Hypothesis DF        SS        MS   F_stat  P_value
---------------------------------------------------------------
                 Group  1 0.0131109 0.0131109 1.0385149 0.31374
              Sequence  1 0.0058638 0.0058638 0.4644731 0.49914
             Treatment  1 0.0011965 0.0011965 0.0947752 0.75964
        Group*Sequence  1 0.0108734 0.0108734 0.8612869 0.35844
          Group*Period  2 0.0160976 0.0080488 0.6375490 0.53340
       Group*Treatment  1 0.0131109 0.0131109 1.0385149 0.31374
Group*Sequence*Subject 44 0.555484  0.0126246 1         0.50000
                 Error 44 0.555484  0.0126246

Partial Tests of Model Effects
            Hypothesis Numer_DF Denom_DF  F_stat   P_value
----------------------------------------------------------
                 Group        1       44 1.0385149 0.31374
              Sequence        1       44 0.4644731 0.49914
             Treatment        1       44 0.0947752 0.75964
        Group*Sequence        1       44 0.8612869 0.35844
          Group*Period        2       44 0.6375490 0.53340
       Group*Treatment        1       44 1.0385149 0.31374
Group*Sequence*Subject       44       44 1         0.50000


N: ΣnG = 48
G: 2
Numerator DF: G – 1 = 1
Denominator DF: N - 2G = 44
F: 0.0131109/0.0126246 = 1.0385149
round(pf(1.0385149, 1, 44, lower.tail=FALSE), 5)
# [1] 0.31374

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