The smaller a study, the more un­cer­tain its results [Study As­sess­ment]

posted by Helmut Homepage – Vienna, Austria, 2014-07-08 19:39 (3603 d 14:56 ago) – Posting: # 13244
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❝ In the study, six subjects dropped out due to different reasons.

❝ Therefore, only 22 evaluable subjects were available for PK calculations and BE evaluation.

6/28 – that’s a lot! Which were the “different reasons”? How many subjects did complete each sequence? The latter information is only important if n1  n2 (imbalanced sequences).

❝ Whether this had resulted in higher Intrasubject variability and due to which the study may have failed?

Possible, but unlikely. With your remaining sample size the CVs and ratios should be pretty “stable”. To give you an impression we can calculate confidence limits of the CV. Let’s assume two cases: A CV of 28% obtained from 28 and 22 subjects; upper CL, α 0.2:
   n  CL of CV (%) 
  28     32.26     
  22     33.03     

As expected the estimate from 28 subjects is more precise (lower upper CL), but the gain compared to 22 subjects is not dramatic.

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