Jacob Cohen thought it would be much more appropriate if we could have a level of concordance, where zero always meant the measure of the agreement expected by chance, and 1 always meant a perfect match. This result can be achieved by the following amount: The missing data is omitted by list. The use of the advanced agreement as a percentage (tolerance!-0) is only possible for numerical values. If tolerance is z.B. 1, spleens that differ by one degree of scale are considered consenting. Consider the emergency table below to explain how the observed and expected agreement is calculated. Two clinical psychologists were asked to diagnose whether 70 people are depressed or not. There are a few words that psychologists sometimes use to describe the degree of agreement between counselors, based on the Kappa value they obtain. These words are: Traditionally, the reliability of Inter-Rater has been measured as a simple total percentage agreement, calculated as the number of cases where the two councillors agree, divided by the total number of cases taken into account. The share of the observed agreement (PF) is the sum of the diagonal proportions corresponding to the proportion of cases in each category for which the two councillors agreed on the assignment.
Cohen, J. 1968. « Weighted Kappa: Nominal Scale Agreement with Provision for Scaled Disagrement or Partial Credit. » S. 70 (4): 213-220. doi:10.1037/h0026256. Part of the agreement observed. The total number of matches observed is the sum of diagonal entries. The proportion of the match observed is: sum (diagonal.values) /N, N being the total number of the table. In our example, the Cohen kappa (k) – 0.65 is a fair to good solidity of compliance according to the Fleiss e al. classification (2003). This is confirmed by the p value obtained (p < 0.05), indicating that our calculated kappa is significantly different from zero. Cohens Kappa (Jacob Cohen 1960, J Cohen (1968)) is used to measure the consent of two advisors (i.e.
« judges, » « observers ») or methods assessed at class scales. This process of measuring the magnitude, in which two advisors assign the same categories or points to the same theme, is called the reliability of the intersplent. This percentage agreement is criticized because it is not able to take into account random or expected agreements by chance, which is the share of the agreement that could be expected to be based simply on chance. Cohens Kappa was calculated to evaluate the agreement between two physicians for the diagnosis of psychiatric disorders in 30 patients. There was a good agreement between the two doctors, kappa – 0.65 (95% CI, 0.46 to 0.84), p < 0.0001. We can now use the "Agreement" command to establish a percentage agreement. The "agreement" command is part of the irr package (in short for Inter-Rater Reliability), so we must first load this package: therefore, on a scale of zero (chance) to a (perfect), your agreement in this example was about 0.75 – not bad! Number of successive rating categories to be considered a tying agreement (see details). Calculates the simple and advanced percentage agreement among advisors. In the example above, there is therefore a significant convergence between the two councillors.
In most applications, Kappa`s size is generally more interested than the statistical significance of Kappa.