Comments on: Bioassay Analysis with the Five Parameter Logistic (5-PL) Non-Linear Regression Curve-Fitting Model

By: Anshuman

Anshuman — Thu, 13 Aug 2009 11:30:08 +0000

Thank you very much for the assistance, as I have to answer to my project incharge about the
calculations associated with the 4PL equation, as I am presently dealing with the ELISA techniques.

By: aliu

aliu — Tue, 11 Aug 2009 18:05:34 +0000

@anshuman: I apologize but I think I initially misread your question. Actually calculating the values for A and D is definitely beyond the scope of this post and is a really complicated process. Essentially, one begins with a “guess” of the parameters and depending on the fit of those parameters the algorithm will try to improve of the initial values and so on and so on. I apologize that this is not really straightforward but that is the reason why we have algorithms and software that do it for us.

By: Anshuman

Anshuman — Tue, 11 Aug 2009 11:23:15 +0000

Thanks for the reply, but then how do one find the values of A and D for the 4PL equation,besides thee values for B and C can be calculated from the graph I suppose. Kindly sight one example and explain.

By: Anonymous

Anonymous — Tue, 11 Aug 2009 11:21:02 +0000

Thanks for the reply, but then how do one find the values of A and D for the 4PL equation,besides thee values values for B and C can be calculated from the graph. Kindly sight one example and explain.

By: aliu

aliu — Mon, 10 Aug 2009 15:54:04 +0000

@anshuman: The concentrations cannot be calculated at A and D because those are the limits of the function. Basically, anything less than or equal to A or greater than or equal to D will be out of limits of the function.

By: anshuman

anshuman — Sat, 08 Aug 2009 12:32:35 +0000

If it is dangerous to extrapolate the grapt then what will the values of A and D in the 4 parameter equation .