Still SF [Two-Stage / GS Designs]

posted by Helmut Homepage – Vienna, Austria, 2016-10-07 08:38  – Posting: # 16704
Views: 10,328

Hi VStus,

lucid words about SF and great ideas about hacking embeded Linux-machines. :-D

I think that TSDs for reference-scaling are not so important compared to ABE. Let us consider two scenarios.
  1. CV higher than expected.
    • ABE
      • In a fixed sample design we loose power.
      • In a TSD with sample size re-estimation we proceed to the second stage and preserve power.
    • RSABE or ABEL
      The acceptance range is scaled and power is maintained.
  2. CV lower than expected.
    • ABE
      • In a fixed sample design we gain power.
      • In a TSD we have some chances to demonstrate BE already in the first stage. Hence, my personal recommendation for n1 75-80% of the fixed sample’s n.
    • RSABE or ABEL
      We loose power until we reach CVwR. Then power increases.

To summarize: In reference-scaling we have to consider lower CVs only. However, the potential impact is over-rated by many. What really hurts (in all designs) is a too optimistic assumption of the GMR.

Cheers,
Helmut Schütz
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