Histogram of ORP mismatch rate (per base) in the BCV control sample. Histograms are compiled for four different read populations: raw, unfiltered ORP reads (black), ORP reads with Q≥ 10, Q≥ 20 and Q≥ 30 shown in blue, green and red, respectively. Left plot shows the number of bases where mismatch frequency is zero for the four read populations. Both the raw and Q10 read pools had 4 bases where the mismatch frequency is zero (black and blue dots on the left panel overlap). Both left and right plots have number of bases as the ordinate.