WinnieH ☆ Sweden, 20230818 10:57 (195 d 13:32 ago) Posting: # 23697 Views: 1,281 

Dear all, I had a question related to the homoscedasticity assumption in the RSABE method when I read the tutorial of PowerTOST. PowerTOSTRSABE If the RSABE method is performed on the highly variable drug with the 4way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? And I think if a 3way crossover design is used, there is no way to assume the homoscedasticity since the test drug is administered once and we can not calculate the WSV of the test drug. A further question is, when do we assume the reference and test product have equal variances, i.e. CVwT ≡ CVwR? And why? Thank you so much and looking forward to your reply! Winnie Edit: Category changed; see also this post #1. [Helmut] 
Helmut ★★★ Vienna, Austria, 20230818 13:23 (195 d 11:06 ago) @ WinnieH Posting: # 23698 Views: 957 

Hi Winnie, ❝ If the RSABE method is performed on the highly variable drug with the 4way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? ❝ And I think if a 3way crossover design is used, there is no way to assume the homoscedasticity since the test drug is administered once and we can not calculate the WSV of the test drug. ❝ A further question is, when do we assume the reference and test product have equal variances, i.e. CVwT ≡ CVwR? And why? If the true CV_{wT} < CV_{wR}, the study will be overpowered, which is economically and ethically questionable. If it will be the other way around, bad luck. See also this article about heteroscedasticity in RSABE and that one for ABEL. — Diftor heh smusma 🖖🏼 Довге життя Україна! _{} Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes 
WinnieH ☆ Sweden, 20230818 15:05 (195 d 09:24 ago) @ Helmut Posting: # 23700 Views: 978 

Thank you so much for the answer and the references . I am looking through them now. Best regards, Zhe Edit: Full quote removed. Please delete everything from the text of the original poster which is not necessary in understanding your answer; see also this post #5! [Helmut] 
BEQool ★ 20230818 14:30 (195 d 09:59 ago) @ WinnieH Posting: # 23699 Views: 946 

❝ I had a question related to the homoscedasticity assumption in the RSABE method when I read the tutorial of PowerTOST. ❝ If the RSABE method is performed on the highly variable drug with the 4way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? And I think if a 3way crossover design is used, there is no way to assume the homoscedasticity since the test drug is administered once and we can not calculate the WSV of the test drug. Hello all, I also have a similar question regarding calculation of s^{2}_{wT } (mentioned in this article about SABE based on the CVw of a Crossover Design). In the article the following equations are stated: And at the end this is written: So my question would be, why cant we get (calculate) s^{2}_{wT } from the partial replicate design? We obviously get s^{2}_{wR } and dont we also get s^{2}_{w } ? So then from the equation marked in yellow in the first picture, we can get s^{2}_{wT } by: (2* s^{2}_{w }  s^{2}_{wR })? Or am I missing something here? Best regards BEQool 
d_labes ★★★ Berlin, Germany, 20230818 16:11 (195 d 08:18 ago) @ BEQool Posting: # 23701 Views: 950 

❝ So my question would be, why cant we get (calculate) s^{2}_{wT } from the partial replicate design? We obviously get s^{2}_{wR } and dont we also get s^{2}_{w } ? So then from the equation marked in yellow in the first picture, we can get s^{2}_{wT } by: (2* s^{2}_{w }  s^{2}_{wR })? Or am I missing something here? Dear BEQool, simply have a look at the sentences following your citation of the formulas in the article about SABE based on the CVw of a Crossover Design) — Regards, Detlew 
BEQool ★ 20230818 19:16 (195 d 05:12 ago) @ d_labes Posting: # 23702 Views: 929 

Dear Detlew, thank you for the answer. I had read the whole article but I am still not getting it Partial replicate design is a crossover design so we can get S^{2}_{W} (and consequently CV_{W}) and because R is replicated we can also get S^{2}_{WR} (and consequently CV_{WR}). So why cant we get S^{2}_{WT} (and consequently CV_{WT}) from the following equation: S^{2}_{W}=(S^{2}_{WT}+S^{2}_{WR})*2 as we only have one unknown (S^{2}_{WT})? "There is an infinite number of combinations of CVwT and CVwR values giving the same pooled CVw. We simply don’t – and can’t – know the variance components. It’s like asking a pupil “We added two numbers and their sum was five. What were the two numbers?” Leaves the pupil – rightly – dazed and confused." > Refering to this, if we know that the sum (S^{2}_{W}) is 5 and one other number (S^{2}_{WR}; lets say it is 3), we can get the unknown number (S^{2}_{WT}; in this case we get 2)? BEQool 