DescTools (version 0.99.15)

KendallW: Kendall's Coefficient of Concordance W

Description

Computes Kendall's coefficient of concordance as an index of interrater reliability of ordinal data. The coefficient could be corrected for ties within raters.

Usage

KendallW(ratings, correct = FALSE, test = FALSE, na.rm = FALSE)

Arguments

ratings

$n \times m$ matrix or dataframe, k subjects (in rows) m raters (in columns).

correct

a logical indicating whether the coefficient should be corrected for ties within raters.

test

a logical indicating whether the test statistic and p-value should be reported.

na.rm

logical, indicating whether NA values should be stripped before the computation proceeds. If set to TRUE only the complete cases of the ratings will be used. Defaults to FALSE.

Value

• Either a single value if test is set to FALSE or else a list with class htest containing the following components:
• statistic
  the value of the chi-square statistic.
• p.value
  the p-value for the test.
• method
  the character string Kendall's coefficient of concordance W.
• data.name
  a character string giving the name(s) of the data.
• estimate
  the coefficient of concordance.
• parameter
  the degrees of freedom df, the number of subjects examined and the number of raters.

Details

Kendall's W should be corrected for ties, if raters did not use a true ranking order for the subjects. The test for the significance of Kendall's W is only valid for large samples.

References

Kendall, M.G. (1948) Rank correlation methods. London: Griffin.

See Also

cor, KappaM, CronbachAlpha, ICC

Examples

anxiety <- data.frame(rater1=c(3,3,3,4,5,5,2,3,5,2,2,6,1,5,2,2,1,2,4,3),
                      rater2=c(3,6,4,6,2,4,2,4,3,3,2,3,3,3,2,2,1,3,3,4),
                      rater3=c(2,1,4,4,3,2,1,6,1,1,1,2,3,3,1,1,3,3,2,2))

KendallW(anxiety, TRUE)

# with test results
KendallW(anxiety, TRUE, test=TRUE)