For both groups we combined all the answers in which subjects gave the same confidence assessment and calculated how often they were right. Good calibration means that the fraction of correct answers should be about equal to the stated confidence level. For example, on questions where subjects said they were 80 percent confident, they should be right about 80 percent of time. If subjects are well calibrated, then a graph of the percent correct against the confidence levels should lie near a 45◦ line. Points below the line would represent overconfidence and points abovewould showunderconfidence. Fig. 1 contains these scatters for both older and younger subjects, along.
