Brajnik, Yesilada and Harper (2011) studied if expertise in accessibility evaluation mattersand found that depending on the metric used it does. They also found that single expertcan identify about 72% of accessibility problems, two can reach 94% and three expertscan cover all of the problems. In comparison at least 14 nonexperts would be necessaryto identify all true problems and one expert could only identify about an average of 50% ofthe problems. This study also shows that experts spend much less time on the evaluationwhile being more confident on the results.