TOST != treatment effect [Power / Sample Size]

posted by mittyri  – Russia, 2025-02-20 14:13 (483 d 08:22 ago) – Posting: # 24367
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Hi BEQool,

❝ ❝ A significant treatment effect will show up in all studies where the confidence interval does not include unity.


❝ Is this always true? Or better, in which cases this isnt true? What could be the reason? Namely I saw a case with lower limit of 90% CI of 102.3% and p-value for treatment effect of 0.055.

❝ So based on 90% CI, treatment effect should be significant but here it isnt :confused:


I guess it is not.
The TOST procedure is designed for equivalence testing and uses two one‑sided tests at the 5% level (each tail), which, when combined, yield a 90% CI. In contrast, a standard test for a treatment effect (ANOVA based) is typically a two‑sided test at the 5% significance level. These two approaches, while related, test slightly different hypotheses.

Kind regards,
Mittyri

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