Correlation model. Suppose we have three duplicated samples 1, 2 and 3 assayed at 6 antibodies B1 - B6. Denoting the aliquot pairs of the samples as 1a, 1b, 2a, 2b, 3a and 3c (see table above), to check the within sample concordance we look at correlations between the 6 pairs of 3 dimensional vectors. That is for each of the antibodies B1, B2 and B3, we determine the correlation between the black and light-grey vectors. Similarly for antibodies B2, B4 and B6 we look at the correlation between the white and dark-grey vectors.