Four Parameter Logistic And Log-Logit; Quantitative Curve Fit Results - Thermo Scientific Varioskan User Manual

Data Processing Parameters
Quantitative curve fit
Four parameter logistic and
Quantitative Curve Fit
158 Thermo Scientific SkanIt
Extrapolation is not available for the cubic spline fit type. Only the means
of the measured calibrator replicates can be used, not the individual replicate
values.
The four-parameter logistic and Log-Logit logistic methods use the same
Log-Logit
fit model:
In the equation above, y is the signal, x the concentration, a the minimum
signal (asymptote below), d the maximum signal (asymptote above), c the
concentration at the inflection point, and b a slope-related term at the
inflection point.
The minimum number of calibrators for these fit types is four.
• Four-parameter logistic fit type. The coefficients of the function are
solved using the Levenberg-Marguardt method.
• Log-Logit fit type. The a and d coefficients are treated as known,
otherwise it is the same as the four-parameter logistic (4PL) fit type.
The Conc. logarithmic transformation is not available for these fit types.
The graph view of the calculation results displays the calculated fit function
results
and its parameters as well as the correlation coefficient R
the graph shows the calibrators used for defining the curve fit. The column
Residual shows the difference between the calculated and actual values.
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