Reproducibility of grouped data assessed by intraclass correlation coefficient - eAppendix
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چکیده
Here, μ represents the overall mean, βi is the deviation of respondent i from the overall mean, and εij is the deviation of i-th respondent’s reported value from his true value, μ+ βi, on occasion j. βi and εij are independent normal with mean 0 and variance σ β and σ , respectively. The intraclass correlation coefficient (ICC) ρ is calculated as share of between-class variability σ β in total variability, ρ = σ β/(σ 2 β + σ ). Defined as a ratio of variances, it ranges from 0 to 1, with higher values indicating better reproducibility. In the case of continuous data, parameters μ, σ β and σ 2 are obtained by maximizing the log-likelihood function. For grouped data, we derive likelihood in the following section. Optimization details are given in sections 3 and 5. We provide implementation in the R package iRepro (available from http://www.imi.hr/~jkovacic/irepro. html).
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