Paired design [General Sta­tis­tics]

posted by Helmut Homepage – Vienna, Austria, 2016-07-28 13:09 (3123 d 17:26 ago) – Posting: # 16525
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Hi ElMaestro & Silva,

❝ ❝ In a crossover study using only one sequence (RT for ex.) […]



This is not a crossover but a paired design.

❝ There is no sequence effect here because Sequence only has one level.

❝ Period and Treatment will have the same meaning;


Right.

❝ But are you sure this is a design you really want to use???


The only application of a paired design I’m aware of is to assess whether PK is linear by comparing AUC0–τ (steady state = T) with AUC0–∞ (single dose = R). Nobody would perform such a study as a crossover since the logistics would be terrible. ElMaestro correctly stated

❝ Period and Treatment will have the same meaning;


Hence, it should be unambiguously stated in the protocol that the model assumes (!) no period effect, i.e., the difference is related solely to the treatment. Contrary to a crossover where period effects mean out (unless sequences are extremely unbalanced) in a paired design great care must be taken to avoid a true period effect – which would confound the treatment effect.
Stupid example: No air conditioning in the clinics and a heat wave during SD. ;-)

@Silva: Is this was you are planning?

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