intraclass correlation coefficient
說明
Intraclass correlation coefficient (ICC)是一個被廣泛使用的信度指標。它可以被使用在再測信度、評分者間信度以及評分者內信度。它可以反應多個測量(評分)結果的相關(correlation)或同意(agreement)程度。
ICC包含多個不同種類(form),Shrout 與 Fleiss(1979)提出6種,而McGraw與Wong(1996)提出10種。根據Koo與Li(2016)的整理,這些不同種類詳列如#ICC 種類表。仔細看可以發現,某些不同類的ICC計算的公式是一樣的。以McGraw與Wong(1996)的架構為例,常用的 Two-way random effects, absolute agreement, single rater/measurement 和 Two-way mixed effects, absolute agreement, single rater/measurement 計算結果是相同的。
研究者應根據研究目的選擇適合的種類。Koo與Li(2016)依照McGraw與Wong(1996)的分類概念提出#ICC選擇流程圖,按照以下4個問題的答案進行選擇:
- 是否所有的被評分樣本都是被同一組的評分者所評分?Do we have the same set of raters for all subjects?
- 評分者樣本是從某個大群體中隨機選取的,還是特定的評分者樣本?Do we have a sample of raters randomly selected from a larger population or a specific sample of raters?
- 我們關注的是各個評分者的信度,還是多個評分者平均值的信度?Are we interested in the reliability of single rater or the mean value of multiple raters?
- 我們關心的是一致性還是同意度?Do we concern about consistency or agreement?
結果解釋
依據Koo與Li(2016)
ICC Value | Reliability |
---|---|
< 0.5 | Poor reliability |
0.5 - 0.75 | Moderate reliability |
0.75 - 0.9 | Good reliability |
> 0.9 | Excellent reliability |
R程式碼
psych package
psych::ICC
計算是按照Shrout 與 Fleiss(1979)的架構,結果會得到6種ICC的結果。
library(psych)
ICC(x, missing=TRUE, alpha=.05, lmer=TRUE,
check.keys=FALSE)
irr package
irr::icc
的計算則是按照McGraw與Wong(1996)的架構,需要設定model
、type
、unit
。
library(irr)
icc(ratings, model = c("oneway", "twoway"),
type = c("consistency", "agreement"),
unit = c("single", "average"), r0 = 0,
conf.level = 0.95)
附錄
ICC 種類表
McGraw and Wong (1996) Convention | Shrout and Fleiss (1979) Convention | Formulas for Calculating ICC |
---|---|---|
One-way random effects, absolute agreement, single rater/measurement | ICC (1,1) | |
Two-way random effects, consistency, single rater/measurement | - | |
Two-way random effects, absolute agreement, single rater/measurement | ICC (2,1) | |
Two-way mixed effects, consistency, single rater/measurement | ICC (3,1) | |
Two-way mixed effects, absolute agreement, single rater/measurement | - | |
One-way random effects, absolute agreement, multiple raters/measurements | ICC(1,k) | |
Two-way random effects, consistency, multiple raters/measurements | - | |
Two-way random effects, absolute agreement, multiple raters/measurements | ICC (2,k) | |
Two-way mixed effects, consistency, multiple raters/measurements | ICC (3,k) | |
Two-way mixed effects, absolute agreement, multiple raters/measurements | - |
說明: