XH7081 ☆ 20220921 22:22 (134 d 20:44 ago) Posting: # 23311 Views: 1,163 

Hello! First of all thank you for the wonderful PowerTOST package! If I want to design an injection site study to compare the relative bioavailability at 3 different injection site, say T1, T2 vs R, in either crossover design or parallel design, is it correct to use the R code below: 1. Crossover design (3x6x3), assuming true theta=1, intraCV=0.3. R results indicate I need 42 total subjects (7 subjects per sequence), not considering drop out etc. Is it correct? > sampleN.TOST(theta0=1, CV=0.3, design="3x6x3",targetpower=0.9) +++++++++++ Equivalence test  TOST +++++++++++ Sample size estimation  Study design: 3x6x3 crossover logtransformed data (multiplicative model) alpha = 0.05, target power = 0.9 BE margins = 0.8 ... 1.25 True ratio = 1, CV = 0.3 Sample size (total) n power 42 0.929519 I also saw some posts suggest doing "two at a time" test, which will use the 2x2 design as follows (which gave essentially the same sample size as the 3x6x3 design above since I need to round up to 6X, so 40 becomes 42). Is this thought process correct? > sampleN.TOST(theta0=1, CV=0.3, design="2x2",targetpower=0.9) +++++++++++ Equivalence test  TOST +++++++++++ Sample size estimation  Study design: 2x2 crossover logtransformed data (multiplicative model) alpha = 0.05, target power = 0.9 BE margins = 0.8 ... 1.25 True ratio = 1, CV = 0.3 Sample size (total) n power 40 0.909560 2. Parallel design (3 arms, assuming true theta=1, pooled CV=0.4). R results indicate I need 132 total subjects (44 subjects per arm), not considering drop out etc. Is it correct, or the 132 is for 2 arms (66 per arm) and I actually need 198 total subjects? > sampleN.TOST(alpha = 0.05, + CV = 0.40, theta0 = 1, + targetpower = 0.90, design = "parallel") +++++++++++ Equivalence test  TOST +++++++++++ Sample size estimation  Study design: 2 parallel groups logtransformed data (multiplicative model) alpha = 0.05, target power = 0.9 BE margins = 0.8 ... 1.25 True ratio = 1, CV = 0.4 Sample size (total) n power 132 0.904103 Many thanks! 
dshah ★★ India/United Kingdom, 20220922 00:08 (134 d 18:58 ago) @ XH7081 Posting: # 23312 Views: 994 

Dear XH7081! Kindly consider True ratio as 0.91.111 instead of 1. Regards, Divyen 
XH7081 ☆ 20220922 19:14 (133 d 23:52 ago) @ dshah Posting: # 23316 Views: 912 

❝ Kindly consider True ratio as 0.91.111 instead of 1. Hi Divyen, thank you for the input. Besides changing the true ratio, are the rest of the code in general correct? 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] 
Helmut ★★★ Vienna, Austria, 20220922 11:30 (134 d 07:36 ago) @ XH7081 Posting: # 23313 Views: 938 

Hi XH7081, ❝ First of all thank you for the wonderful PowerTOST package! Welcome. THX to Detlew Labes and Benjamin Lang. Both did much more than myself. ❝ If I want to design an injection site study to compare the relative bioavailability at 3 different injection site, say T1, T2 vs R, in either crossover design or parallel design, is it correct to use the R code below: In principle yes but as already mentioned by Divyen, theta0 = 1 should not be used.❝ I also saw some posts suggest doing "two at a time" test, which will use the 2x2 design as follows (which gave essentially the same sample size as the 3x6x3 design above since I need to round up to 6X, so 40 becomes 42). Is this thought process correct? See this article and click on ❝ Parallel design (3 arms, assuming true theta=1, pooled CV=0.4). R results indicate I need 132 total subjects (44 subjects per arm), not considering drop out etc. Is it correct, or the 132 is for 2 arms (66 per arm) and I actually need 198 total subjects? Yes. — 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 
XH7081 ☆ 20220922 19:13 (133 d 23:53 ago) @ Helmut Posting: # 23315 Views: 901 

❝ ❝ Parallel design (3 arms, assuming true theta=1, pooled CV=0.4). R results indicate I need 132 total subjects (44 subjects per arm), not considering drop out etc. Is it correct, or the 132 is for 2 arms (66 per arm) and I actually need 198 total subjects? ❝ ❝ Yes. Thank you for your reply. Just to clarify, when you say "Yes", do you mean that total of 132 subjects (44 per arm) is correct, or total of 198 subjects (66 per arm) is correct? 
Helmut ★★★ Vienna, Austria, 20220923 13:03 (133 d 06:03 ago) @ XH7081 Posting: # 23317 Views: 869 

Hi XH7081, ❝ Just to clarify, when you say "Yes", do you mean that total of 132 subjects (44 per arm) is correct, or total of 198 subjects (66 per arm) is correct? The latter. The sample size functions of PowerTOST give always the total sample size. Therefore, 132 / 2 × 3 = 198. Sorry for the confusion caused.— 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 