WinnieH ☆ Sweden, 2023-08-18 10:57 (482 d 05:11 ago) Posting: # 23697 Views: 2,777 |
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Dear all, I had a question related to the homoscedasticity assumption in the RSABE method when I read the tutorial of PowerTOST. PowerTOST-RSABE If the RSABE method is performed on the highly variable drug with the 4-way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? And I think if a 3-way 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, 2023-08-18 13:23 (482 d 02:45 ago) @ WinnieH Posting: # 23698 Views: 2,133 |
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Hi Winnie, ❝ If the RSABE method is performed on the highly variable drug with the 4-way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? ❝ And I think if a 3-way 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 CVwT < CVwR, 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. — Dif-tor 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, 2023-08-18 15:05 (482 d 01:03 ago) @ Helmut Posting: # 23700 Views: 2,153 |
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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 ★ 2023-08-18 14:30 (482 d 01:38 ago) @ WinnieH Posting: # 23699 Views: 2,121 |
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❝ 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 4-way crossover design (not the NTI drug), is the homoscedasticity assumption always holden? And I think if a 3-way 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 s2wT (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) s2wT from the partial replicate design? We obviously get s2wR and dont we also get s2w ? So then from the equation marked in yellow in the first picture, we can get s2wT by: (2* s2w - s2wR )? Or am I missing something here? Best regards BEQool |
d_labes ★★★ Berlin, Germany, 2023-08-18 16:11 (481 d 23:57 ago) @ BEQool Posting: # 23701 Views: 2,148 |
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❝ So my question would be, why cant we get (calculate) s2wT from the partial replicate design? We obviously get s2wR and dont we also get s2w ? So then from the equation marked in yellow in the first picture, we can get s2wT by: (2* s2w - s2wR )? 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 ★ 2023-08-18 19:16 (481 d 20:52 ago) @ d_labes Posting: # 23702 Views: 2,103 |
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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 S2W (and consequently CVW) and because R is replicated we can also get S2WR (and consequently CVWR). So why cant we get S2WT (and consequently CVWT) from the following equation: S2W=(S2WT+S2WR)*2 as we only have one unknown (S2WT)? "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 (S2W) is 5 and one other number (S2WR; lets say it is 3), we can get the unknown number (S2WT; in this case we get 2)? BEQool |