Chance Agreement Betekenis


Cohen J. Weighted kappa: the nominal scale agreement with provisions on differences of opinion or partial appropriations. Psychol Bull 1968; 70:213-20. Landis RJ, GG Chief. The measure of the compliance agreement for categorical data. Biometrics 1977; 33: 159-74. The use of percentages can lead to two advisors appearing to be very reliable and quite in agreement, even if they have randomly assigned their scores and do not agree at all. Cohens Kappa manages this problem because it takes into account a fortuitous agreement. If the number of categories used is small (z.B. 2 or 3), the probability of 2 advisors agreeing by pure coincidence increases considerably. This is because the two advisors must limit themselves to the limited number of options available, which affects the overall agreement rate, not necessarily their propensity to enter into an “intrinsic” agreement (an agreement is considered “intrinsic” if not due to chance).

Kraayeveld CL, Gijn J van, Schouten HJA, Staal A.Interobserver Accord for the Diagnosis of Transient Ischemic Attacks. STROKE 1984; 15: 723-5. However, comparing studies on the basis of overall compliance creates problems. Table 2 shows 2 2 tables of 2 x 2 tables of surveys on interobserver variations. In both cases, the overall agreement is 90, i.e. 47 43 in Study A and 85 5 in Study B. The observer`s variation is therefore that it ignores the agreement that may result from chance, the fortuitous agreement. The contribution of coincidence chance to overall compliance can be calculated from the limit values of Table 2 x 2 according to the following principle.

Table 2 shows that researchers classify 2,55100 of all observations as abnormal and 45100 as normal. If his judgment were based exclusively on this frequency distribution, he would consider the 49 results that researcher 1 considers different for 55100 and 45100 as normal, respectively 27 and 22. In this way, the expected frequencies based on the edge studs can be calculated in each of the 4 fields.

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