When a patient is examined by a physician, it is desirable that the findings (diagnosis, symptoms) do not change when she is examined by a different physician. The patient is not inspired with confidence if physicians seriously differ in opinion, just because they cannot all be
right. Of course, the foregoing does not only apply to physicians, but applies to judging observers in general, especially in situations where it is impossible to establish the truth in an objective way.
In medical and non-medical scientific research associations between different characteristics (personality aspects, housing conditions, diagnosis, medical history, degree of recovery) may be blurred by errors in the assessment of these characteristics. Thereby important
associations may be overlooked. Associations that are discovered may be hard to interpret because different studies may result in different quantitative conclusions.
The specification of disagreement may be the first step to a better agreement among observers: Which disagreements do frequently occur and which observers often have different opinions? This may lead to a further standardization of the way of judging and to regular training on the basis of difficult cases; this second step, however, is not considered in this book.
The value of judgements, in daily practice and in scientific research, may greatly increase by substantially improved interobserver agreement. For the sake of completeness, however. it must be mentioned that even perfect interobserver agreement does not guarantee that
judgements have any value, Therefore, when simplifying a judgement system, one must avoid to lose important information.