Four Parameter Logistic Curve

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(3 min 24 sec)
4PL

Quantitative analysis of samples using a Four Parameter Logistic (4PL) curve fit suitable for calculating concentrations from symmetrical sigmoidal calibrators. This method is widely used and cited in data analysis for typical ELISAs.

This analysis optionally includes a background correction step. If a blank group is included on your layout, the mean of the blank replicates is first subtracted from the raw data measurements (the corrected values are then used in the fit).

The standard data points (concentration vs. measurement) are plotted on semi-log axes and a 4PL is made through the points. The concentrations of the samples are determined from the fit with any specified dilution factors applied.

Note, the concentration units are unspecified; use whichever units are applicable for your standards (the calculated concentrations will use these same unspecified units).

The %CV, Standard Deviation and Standard Error are calculated for each replicated sample.

Samples outside the range of the standards or the fit (greater than the upper asymptote or below the lower asymptote) are highlighted in yellow.

See also Related assays
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Measurements

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Microplate

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Standard Concentrations

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Dilution Factors

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Sample IDs

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Run Notes