![]() ![]() Similar agreement indices have been proposed by Haber et al. The concept of individual agreement is derived from the idea of individual bioequivalence in bioequivalence studies. An ‘acceptable disagreement’ requires that the differences between measurements of different observers are similar to the differences between replicated measurements of the same observer. Haber, Barnhart and colleagues introduced the coefficients of individual agreement (CIA’s), which are scaled relative to an acceptable disagreement, with the goal of establishing interchangeability of observers. In addition, Shoukri and King and Chinchilli also defined ICC and CCC for qualitative data. However, these coefficients have been shown to be equivalent to the weighted Kappa for categorical data. The ICC and the CCC are originally defined for quantitative data. also showed that the CCC depends on the between-subject variability due to the fact that it is scaled relative to the maximum disagreement defined as the expected MSD under independence. Atkinson and Nevill pointed out that an increase in the between-subject variability results in a larger value of CCC even if the individual differences between measurements by the two methods remain the same. Furthermore, the CCC depends on the between-subject variability. ![]() ![]() However, independence and disagreement are two different concepts. The CCC is based on comparing the mean squared deviation (MSD) to its value under independence. Specifically, if the ANOVA model assumptions are satisfied, the CCC reduces to the agreement ICC defined by this ANOVA model. Under certain conditions, the CCC is equivalent to one version of the ICC. classified the existing methods for evaluation agreement as follows: (1) descriptive tools, such as descriptive statistics and plots, (2) unscaled agreement indices, such as mean squared deviation (MSD), coverage probability (CP) and total deviation index (TDI), and (3) scaled agreement indices.Īmong the scaled agreement indices, the intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) are the most popular. In a recent review paper, Barnhart et al. In medical and other related sciences, many statistical approaches have been proposed for assessing agreement among observers or measurement methods. ![]()
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