Bioequivalence and Bioavailability Forum • Weibull

Weibull [Dissolution / BCS / IVIVC]

posted by Helmut – Vienna, Austria, 2009-12-15 20:54 (6029 d 22:34 ago) – Posting: # 4481
Views: 8,201

Dear Varinder!

Time points in column A
Cumulative % dissolved in Column B
C1: =1-EXP(-F$1*A1^G$1), copy the formula down to all cells containing values in column A (these are the estimated values of the cumulative Weibull-distribution)
D1: =(C1-B1)^2, copy the formula down to all cells containing values in column A (these are the squared residuals)
E1: =SUM(D:D) (this is the sum of squared residuals we want to minimize)
F1: 1 (starting value for alpha)
G1: 1 (starting value for beta)
Fire up the Solver Add-in
Set Cell: $E$1
Equal To: [•] Min
By Changing Target Cells: $F$1:$G$1
Subject to the Constraints: Remove all constraints (if any).
Options...
[X] Assume Non-Negative
OK
Solve

Remark: alpha and beta of the cumulative Weibull-distribution are positive real numbers (>0), therefore the constraints.

Example (Excel 2000 on XP Pro SP3 and Vista Pro SP2):

  t    Qc     fit

  0    0      0

  0.5  0.209  0.204

  1    0.536  0.547

  1.5  0.818  0.806

  2    0.933  0.936 

  2.5  0.974  0.983

gives 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!
Helmut Schütz

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Complete thread:

Weibull varinderkb 2009-12-15 15:44
- WeibullHelmut 2009-12-15 19:54
  - Weibull varinderkb 2009-12-16 14:06
  - Weibull ElMaestro 2009-12-16 16:25
    - Weibull & and beyond Helmut 2009-12-16 18:13
      - the lingo ElMaestro 2009-12-16 18:48
        
        Dissolution Helmut 2009-12-16 19:10