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Why are some of my wells automatically flagged (I am using four-parameter fit)?

Document ID: DQ087
Relevant to following products: Manta WorkOut 1.5 WorkOut 2.0 Stingray
Document description: Why are some of my wells automatically flagged (I am using four-parameter fit)?



The Four Parameter Fit results in a sigmoidal fit with upper and lower asymptotes.

The resulting fit can only be used to calculate measurements within these asymptotes (which are actually the calculated A and D values of the Four Parameter Fit). For measurements outside of this range a concentration cannot be calculated and each out of range well will be flagged.

You can see the valid range of the Four Parameter Fit by looking at the coefficients from the fit and the data.

By default the "Standard Curve Fit" transform calculates the concentrations of all samples, including the standard wells.  It is possible that one or more of your replicates of your lowest and/or highest standards maybe outside of the range of the asymptotes.  In this case the standard wells will be marked as flagged.  This is because the concentration of the standard cannot be calculated from the fit (this is not necessarily important because the concentration is already known - it is a standard!).  All of the standard wells are used in calculating the fit, it is the step where the concentrations are back-fitted onto this curve that the wells are flagged - the wells are flagged after the concentrations are calculated.

When wells are flagged a table is added to the end of the report, this describes exactly why the well is flagged.





Related articles:
DQ065: Which curve fit should I use?
How To: Choose a curve fit method...

DQ117: Which curve fits are available in WorkOut 2.0?
Which curve fits are available in WorkOut 2.0?

DQ145: How do I exclude a standard from a data set?
How To: Flag a point





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