BE study designs [Design Issues]

posted by Helmut Homepage – Vienna, Austria, 2006-01-17 10:27 (6459 d 13:40 ago) – Posting: # 56
Views: 24,503

❝ When you say that chance of regulatory acceptance of 3x3 is close to zero, you mean specifically for 3x3x3, or it is applicable to 3x3x6 design also?

You are right, I was not precise: 3×3×6 is acceptable, whereas 3×3×3 is not.

❝ Also, can you please let me know the reason for the same.

The 3×3×3 does not give us unbiased estimates.
Since we are interested in at least two pairwise comparisons (T1 vs. R, T2 vs. R), it is desirable to get estimates with the same degree of precision. However, to achieve this goal, the design must be balanced. A design is said to be balanced, if (acc. to Jones & Kenward):
  1. Each formulation occurs only once with each subject.
  2. Each formulation occurs the same number of times in each period.
  3. The number of subjects who receive formulation i in some period followed by formulation j in the next period is the same for all i # j.
Williams' designs minimize the number of sequences for a given number of treatments and periods.
Unfortunately for three treatments your sample size has to be a multiple of six, which may be inconvenient in terms of practicability.

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