Table 1.

Within-individual variation is smaller than inter-individual variation in cytosine modification levels across arrays.We compared β-values from the original 450K array to the more recent 450K array results and found that the 3 samples included in both arrays showed a higher level of intra-individual (across different runs) correlation, measured by the correlation coefficient (r) compared with inter-individual correlations of different samples run on the same chip

	Within-individual variation			Inter-individual variation
	GM07055	GM12815	GM12892	GM07055	GM12815	GM12892
GM07055	0.83
GM12815		0.93		0.77
GM12892			0.81	0.69	0.65
GM12878				0.80	0.73	0.64