Normalized Absorbance Ratio refers to find the absorbance values which provides the sample of interest and not the matrix. To calculate each ELISA plate, you must work with blanks or controls of matrix (broth or culture medium), the absorbance of the matrix should be normalized to zero or subtract the absorbance value (results) with the blank value.

How we normalize the experimental error occurring in developing ELISA in several plates?

Hello

in paper by ( Agnihotram V. et al , 2010 ) computed normalized absorbance ratios (NARs) by further correcting the net mean OD value for each sample and dilution by dividing it by the equivalent mean result (blank corrected) from the serum pool included in the same plate in triplicate.

see the attachment , Good luck 

https://www.researchgate.net/post/What_is_meant_by_Normalized_Absorbance_Ratio_in_ELISA?tpr_view=6ac97ec8-3d39-47c9-907c-91cbe646686a_3