Tainted ratings can result from personal biases, idiosyncratic use of categories, and pressure to conform. Judge training and assigning two or more judges to rate each performance are steps towards improving the quality of the ratings - but they are not an automatic solution to rating quality problems. Rerating is one attempt to deal with judging deficiencies. If there is a criterion pass-fail point, then performances just below that level may be rerated and awarded the higher of the two sets or ratings. If all ratings are equally crucial, then a system of paired judging is commonly used.
Every performance is rated by two judges.
Any disagreement of more than one rating point is resolved by having the performance rated by a third judge. Thus judge disagreement causes extra work for the judge panel. This induces judges to minimize the risk of disagreement by increasing the chance that they agree. Disagreement of more than one category is less likely, or even impossible in many cases, when both judges use central categories. The overall effect is to promote conformity and to reduce the flow of possibly useful information among ratings.