Bioequivalence and Bioavailability Forum • Geometric mean and CV

Geometric mean and CV [Power / Sample Size]

posted by Helmut – Vienna, Austria, 2019-09-05 16:05 (1487 d 15:35 ago) – Posting: # 20543
Views: 5,962

Hi Rocco,

❝ I see people will typically enter sample sd / sample mean of the single formulation, but I feel this is incorrect.

You are right. PK metrics like AUC and C_max follow a lognormal distribution and hence, arithmetic means and their SDs / CVs are wrong (i.e., are positively biased).

If you plan for a parallel design you should use the geometric CV.
$$\overline{x}_{log}=\frac{\sum (log(x_i))}{n}$$ $$\overline{x}_{geo}=\sqrt[n]{x_1x_2\ldots x_n}=e^{\overline{x}_{log}}$$ $$s_{log}^{2}=\frac{\sum (log(x_i-\overline{x}_{log}))}{n-1}$$ $$CV_{log}=\sqrt{e^{s_{log}^{2}}-1}$$ Only if you don’t have access to the raw data, you would need simulations.

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Complete thread:

Input for CV when small first-in-man has been run Rocco_M 2019-09-03 18:45 [Power / Sample Size]
- Geometric mean and CVHelmut 2019-09-05 14:05
  - Geometric mean and CV Rocco_M 2019-09-05 23:49
    - Geometric mean and CV Helmut 2019-09-06 00:15
      - Geometric mean and CV Rocco_M 2019-09-06 17:49
        
        Geometric mean and CV Helmut 2019-09-06 18:15
        
        Geometric mean and CV ElMaestro 2019-09-06 19:03
        
        Geometric mean and CV Helmut 2019-09-07 09:57
        
        Geometric mean and CV Rocco_M 2019-09-09 13:31
        
        Assumptions… Helmut 2019-09-09 14:09
        
        Assumptions… Rocco_M 2019-09-09 16:35
        
        Assumptions… Helmut 2019-09-09 17:19
        
        Assumptions… Rocco_M 2019-09-13 21:28
        
        t-test & Welch-test Helmut 2019-09-14 00:16
        
        sampleN.TOST and CI.BE Rocco_M 2019-09-17 22:02
        
        assumptions vs. realizations Helmut 2019-09-18 11:04