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varinderkb ☆ 2009-12-15 16:44 (6028 d 22:08 ago) Posting: # 4480 Views: 9,459 |
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hi please anyone can guide me how to calculate alpha and beta parameters of Weibull from a given in-vitro data using Excel. Edit: Category changed. [Helmut] |
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Helmut ★★★   Vienna, Austria, 2009-12-15 20:54 (6028 d 17:58 ago) @ varinderkb Posting: # 4481 Views: 8,199 |
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Dear Varinder!
Example (Excel 2000 on XP Pro SP3 and Vista Pro SP2): t Qc fitgives alpha 0.7908, beta 1.796, and an SSQ of 0.000388691. BTW, Excel is a terrible piece of software - especially the solver-routine. Consider opting for real software. — 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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varinderkb ☆ 2009-12-16 15:06 (6027 d 23:46 ago) @ Helmut Posting: # 4482 Views: 8,245 |
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Hi Thanks for quick and kind response with regards Varinder Kumar  |
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ElMaestro ★★★ Denmark, 2009-12-16 17:25 (6027 d 21:27 ago) @ Helmut Posting: # 4483 Views: 8,177 |
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Hi HS, "Since neither measured nor estimated dissolution percentage should assume negative values there might be a constraint on the error distribution that speaks against using minimisation of sums of squares for estimation of alpha and beta. The applicant should qualify...."  OK, sorry, could not help it. I am unfortunately too unfamiliar with dissolution (or the Excel solver) but do you have a ref. to a work using the equation you have fitted the data to? ❝ BTW, Excel is (...) real software. Yeah, I love it too. Merry Xmas. EM. |
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Helmut ★★★ Vienna, Austria, 2009-12-16 19:13 (6027 d 19:40 ago) @ ElMaestro Posting: # 4484 Views: 8,259 |
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Dear ElMaestro! ❝ "Since neither measured nor estimated dissolution percentage should assume negative values there might be a constraint on the error distribution that speaks against using minimisation of sums of squares for estimation of alpha and beta. The applicant should qualify...." Wonderful! Do you quote from your memory? The style sounds familiar to me (aka ‘old sock’). Next time I fit PK-data to a multiexponential model, I will not state that I use constraints (≥0 for coefficients and ≤0 for exponents).  ❝ I am unfortunately too unfamiliar with dissolution (or the Excel solver) but do you have a ref. to a work using the equation you have fitted the data to? The equation is the CDF of the Weibull-distribution. Other empirical models in dissolution are the CDF of the exponential (\(\small{y=1-\exp (-\alpha\cdot x)}\), where \(\small{\alpha >0}\)), Higuchi (\(\small{y=\alpha\cdot \sqrt{x}}\)), Korsmeyer–Peppas (\(\small{y=\alpha\cdot \exp (1/\beta)}\)), … Reference? Hhm, dissolution is not my cup of tea. But have a look at Dissolution Technologies (back issues). ❝ ❝ BTW, Excel is (...) real software. Yes, Sir! I’m also unfamiliar with Excel’s solver… — 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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ElMaestro ★★★ Denmark, 2009-12-16 19:48 (6027 d 19:04 ago) @ Helmut Posting: # 4485 Views: 8,099 |
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Dear HS, ❝ Wonderful! Do you quote from your memory? The style sounds familiar (...) You know I speak Flemish and I talk dirty. In addition, I have over the years picked up a little bit of the regulatory syntax. This was just an improvisation. I think I will need to read some more about dissolution. It seems it is becoming more and more important in a quantitative way, due to biowaivers and ivivc's. To me all this is pretty obscure. But now I am going off topic, so will stop here and start reading. EM. |
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Helmut ★★★ Vienna, Austria, 2009-12-16 20:10 (6027 d 18:43 ago) @ ElMaestro Posting: # 4486 Views: 8,087 |
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Dear ElMaestro! ❝ To me all this is pretty obscure. Dazed and confused? If you have some spare money (haha) consider attending one of Jean-Michel’s workshops. — 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