Improved robustness in the QCC in simulated ChIP-chip data. A comparison of different correlation coefficients (the Pearson, the Spearman, and the Quantized) as a function of signal coverage, for SNR values of 3, 4, and 5, respectively for (A), (B), and (C). The number of initial bins is 100. The QCC is less sensitive to signal coverage as the nearly flat profile indicates, but it is still sensitive to data quality (i.e., the SNR in the simulated data). Each point is an average over 100 simulated replicate pairs; error bars represent a 95% confidence interval.