Bioequivalence and Bioavailability Forum • Parallel designs (total variance)

Parallel designs (total variance) [Power / Sample Size]

posted by Helmut – Vienna, Austria, 2007-07-20 18:29 (6558 d 09:51 ago) – Posting: # 917
Views: 27,498

Dear Nav!

❝ I have data from a parallel pilot study and am using that to estimate the sample size for a pivotal study. The formula that I am using requires an estimate of the inter subject variability which I don't have. I have the total variability (sqrt(MSE)). Is there a way to estimate intersubject variability from a parallel design or would it be correct to use the total variability instead?

Hhm, yes you have the total variability (inter- + intra-subjects); the same will be true for your pivotal study. I don’t get your point of trying to estimate inter-subject variability from total. Which formula are you referring to?

❝ Would it be correct to estimate inter-subject var as sd/mean for test and reference separately and then take the average?

❝

❝ And one last question, how correct is it to take 60% of inter subject (calculated as sd/mean) to be the intrasubject variability?

I don’t think so (both questions).

For an example please have a look at
Chow SC, Wang H. On Sample Size Calculation in Bioequivalence Trials. J Pharmacokin Pharmacodyn. 2001;28(2):155-69.
and Errata given at
J Pharmacokin Pharmacodyn. 2002;29(1):101-2.

You will also need two letters to the editor:
Hauschke D. A Note on Sample Size Calculation in Bioequivalence Trials. J Pharmacokin Pharmacodyn. 2002;29(1):89-94.
Blood P. Sample Size Calculation in Bioeqivalence Trials. J Pharmacokin Pharmacodyn. 2002;29(1):95-7.
H Wang H, SC Chow SC. Authors’ Response. J Pharmacokin Pharmacodyn. 2002;29(1):99.

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Complete thread:

Sample size estimation for parallel design Nav Coelho 2007-07-20 16:14
- Parallel designs (total variance)Helmut 2007-07-20 16:29
  - Parallel designs (total variance) Nav Coelho 2007-07-20 18:38
    - CV-intra # 60% CV-inter Helmut 2007-07-22 01:17
    - total (pooled) variance: examples Helmut 2007-07-23 17:44
      - total (pooled) variance: examples Nav Coelho 2007-07-23 19:58
      - total (pooled) variance: examples BEQool 2023-04-18 09:59
        
        Higher-Order Crossovers Helmut 2023-04-20 10:19
        
        Higher-Order Crossovers BEQool 2023-04-21 07:53
        
        total (pooled) variance: examples zizou 2023-04-21 21:23
        
        total (pooled) variance: examples BEQool 2023-04-22 18:20
        
        total (pooled) variance: examples zizou 2023-04-22 21:06
        
        total (pooled) variance: examples BEQool 2023-04-25 10:57
        
        total (pooled) variance: examples zizou 2023-04-25 22:43
        
        total (pooled) variance: examples BEQool 2023-05-04 08:17
- Sample size estimation for parallel design Dipesh Jayswal 2007-07-24 08:52