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john john ☆ Spain, 2015-05-13 15:36 (3601 d 08:55 ago) Posting: # 14803 Views: 13,959 |
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hi Knowing the intrasubject variability is there any way to extrapolate the intersubject variability? Thanks. Edit: Category changed; see also this post #1. [Helmut] |
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Helmut ★★★   Vienna, Austria, 2015-05-13 16:33 (3601 d 07:57 ago) @ john john Posting: # 14804 Views: 12,729 |
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Hi John John, ❝ Knowing the intrasubject variability is there any way to extrapolate the intersubject variability? No. There is no relationship between those. For examples see the end of this post. Please forget CVinter. In planning a crossover study you need CVintra and for a parallel study CVtotal. ![[image]](img/uploaded/image649.png) In 2012 I reviewed a manuscript claiming such a relationship (well: The other way ’round – estimating CVintra from CVtotal). All [sic] reviewers rejected the manuscript.Obviously the authors were more successful in a journal with a lower impact factor… I think that it’s crap, but if you want to have a look: Ramírez E, Abraira V, Guerra P, Borobia AM, Duque B, López JL, Mosquera B, Lubomirov R, Carcas AJ, Frías J. A Preliminary Model to Avoid the Overestimation of Sample Size in Bioequivalence Studies. Drug Res. 2013;63(2):98–103. doi:10.1055/s-0032-1333296. — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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nobody nothing 2015-05-13 16:53 (3601 d 07:37 ago) @ Helmut Posting: # 14805 Views: 12,607 |
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OT: Again Drug Res. ? :-O notorious... — Kindest regards, nobody |
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Helmut ★★★ Vienna, Austria, 2015-05-13 17:11 (3601 d 07:19 ago) @ nobody Posting: # 14806 Views: 12,489 |
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Hi nobody, ❝ OT: Again Drug Res. ? :-O notorious... Yessir. Decades ago “Arzneimittelforschung” (founded in 1951!) had a good reputation. Gone with the wind (IF 0.507). The authors of the MS tried it first at a journal with an IF of 2.037.  — 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 |
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nobody nothing 2015-05-13 17:18 (3601 d 07:13 ago) @ Helmut Posting: # 14807 Views: 12,386 |
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When I was young Arznei-Frosch (sic!) was the standard for some things (at least in Germany, but also internationally...) Times change (quickly). — Kindest regards, nobody |
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Helmut ★★★ Vienna, Austria, 2015-05-13 17:29 (3601 d 07:01 ago) @ nobody Posting: # 14808 Views: 12,443 |
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Hi nobody, ❝ Arznei-Frosch (sic!)  When I was young sex was safe and I recorded my favorite songs off the radio onto Compact Cassettes. — 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 |
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nobody nothing 2015-05-13 17:37 (3601 d 06:53 ago) @ Helmut Posting: # 14809 Views: 12,531 |
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Sex was never really safe but... ![[image]](https://www.ruempelstilzchens-laden.de/content/136-a-big.jpg) — Kindest regards, nobody |
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john john ☆ Spain, 2015-05-14 14:16 (3600 d 10:14 ago) @ Helmut Posting: # 14815 Views: 12,388 |
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Hi Helmut In a bioavailability study with six healthy volunteers: ...(Cmax; range 135–422 ng ml-') and time to maximum (tmax; range 1.5–7.0 h) for the three tablet doses showed significant differences between subjects (P <0.009; between subject coefficients of variation (CVs) 34% and 27%, respectively). There were no within subject differences in C, (P = 0.32; mean within subject CV 11% To calculate the sample size for a parallel study I use the total CV= 45? or do I need the pooled variability? Which is? Thanks Edit: Merged with a later post. Don’t fork; you can edit your post with 24 hours. [Helmut] |
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Helmut ★★★ Vienna, Austria, 2015-05-15 15:05 (3599 d 09:25 ago) @ john john Posting: # 14827 Views: 12,382 |
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Hi John John, ❝ In a bioavailability study with six healthy volunteers: I would never plan a pivotal study based on results of such a small pilot – especially if the variability is high. Let’s assume a CV of 30%. From six subjects we can calculate a confidence interval of the CV with 18–102%. Not meaningful. ❝ ...(Cmax; range 135–422 ng ml-') and time to maximum (tmax; range 1.5–7.0 h) for the three tablet doses showed significant differences between subjects (P <0.009; between subject coefficients of variation (CVs) 34% and 27%, respectively). There were no within subject differences in C, (P = 0.32; mean within subject CV 11% The quoted text leaves many questions open. I guess it was a crossover. Significant differences between subjects… Why report this at all? Since we know that results come from different subjects, this effect will ![[image]](img/uploaded/image485.png) Two values for CVinter? How were those calculated? From the ANOVA you get only one. Some people use the (arithmetic!) SD/mean of treatments (like in the crappy paper above). Has nothing to do with the ANOVA on log-transfomed data.❝ To calculate the sample size for a parallel study I use the total CV= 45? No way! CVs are not additive (CVpooled ≠ CVintra + CVinter). See the methylphenidate example from this post.
❝ or do I need the pooled variability? Yes. ❝ Which is? Not the slightest idea. Not accessible from what you posted. You need either the complete ANOVA or the raw data. — 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 |
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john john ☆ Spain, 2015-05-15 15:13 (3599 d 09:18 ago) @ Helmut Posting: # 14828 Views: 12,295 |
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Hi Helmut But how I find MSe and MSs? Thanks |
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Helmut ★★★ Vienna, Austria, 2015-05-15 15:14 (3599 d 09:16 ago) @ john john Posting: # 14829 Views: 12,225 |
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Hi John John, ❝ But how I find MSe and MSs? They are given in the ANOVA of a crossover study. — 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 |
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john john ☆ Spain, 2015-05-15 15:50 (3599 d 08:40 ago) @ Helmut Posting: # 14830 Views: 12,259 |
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❝ They are given in the ANOVA of a crossover study. But as hydroxychloroquine has a half-life of elimination of about 50 days, studies are made in parallel, so I don’t have that data. 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] |
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Helmut ★★★ Vienna, Austria, 2015-05-15 16:07 (3599 d 08:23 ago) @ john john Posting: # 14831 Views: 12,350 |
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Hi John John, ❝ But as hydroxychloroquine has a half-life of elimination of about 50 days, studies are made in parallel, so I don’t have that data. Heck, this is not the topic of this thread. I gave you some examples in the other thread. CVtotal was reported with ~30–35%, both for AUC and Cmax. From the ANOVA of a parallel design use \(\small{CV_\textrm{total}(\%)=100\sqrt{\exp(MSE)-1}}\). — 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 |
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john john ☆ Spain, 2015-05-15 17:07 (3599 d 07:23 ago) @ Helmut Posting: # 14833 Views: 12,153 |
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Hi Helmut For complicate things further: if I do not have the ANOVA, it would be justified to use the sum of CVintra and CVinter, or only CVinter? Thanks |
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Helmut ★★★ Vienna, Austria, 2015-05-15 17:10 (3599 d 07:20 ago) @ john john Posting: # 14834 Views: 12,328 |
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Hi John John, ❝ […] it would be justified to use the sum of CVintra and CVinter, or only CVinter? Did you read my posts – or at least their subjects lines? Are you a troll? EOD from my side. — 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 |
Ing. Helmut Schütz