Determine the precision of your method at different levels of dilution.

The following image from the 'Linearity of dilution assessment' sample document shows results for an undiluted Test sample and three dilutions of the undiluted sample. Predilution factors are assigned to the diluted samples. The concentration is defined as the determined concentration of the undiluted sample.

Note how the interpolation results show the difference between the working concentration of the Test sample on the plate and the absolute concentration of the undiluted Test sample.