Quality calibration curves for AYB and Ibis. Quality calibration curves for AYB (left) and Ibis (right) on the Ibis Test data set of 200K 50 cycle reads. For each base-caller, two graphs are superimposed: a line chart with error bars showing how the empirical quality changes with estimated quality (left axis) and a histogram of how many bases have a given estimated quality (right axis, as a proportion of mapped bases). The error bars represent 99% confidence intervals, obtained by transforming the Wilson interval  for the proportion into a quality score. On each graph, straight lines are shown representing perfect correlation between estimated and empirical qualities (solid) and the best linear weighted fit (dashed).