Simulations mandatory [Two-Stage / GS Designs]

posted by Helmut Homepage – Vienna, Austria, 2024-01-09 10:31 (186 d 07:41 ago) – Posting: # 23824
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Hi Achievwin,

❝ Thank you for your nice reply.

Welcome.

Just to be clear: Some authors (right now I’m reviewing a manuscript submitted to Stat Med…) believe (‼) that Pocock’s \(\small{\color{Blue}{\alpha_\text{adj}=0.0294}}\) (94.12% CI) is ‘uni­versally’ valid – even for reference-scaling of HVDs. This is a gross misunderstanding and not even wrong. It was derived for superiority testing in a GSD (fixed sample size N) with one interim at – exactly – N/2 and known variances. The fact that it controlled the Type I Error in Pot­vin’s Method B (TSD in a 2×2×2 design) was a mere lucky punch.
In my example I needed \(\small{\color{Red}{\alpha_\text{adj}=0.0274}}\) (94.52% CI) to control the Type I Error.

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