Cluster-level reproducibility of data from different laboratories. Two laboratories independently produced ChIP-chip data for CTCF in Drosophila S2 cells. (A) A scatterplot between the two datasets for the probes on the X chromosome (only 3000 points are shown for legibility). (B) After quantization (with jittering to view data points that would otherwise be overlapping). (C) Cluster-level concordance at varying quantile thresholds. The maximum of the cluster-level correlations is 0.546.