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Last data update: 2014.03.03

R: Within-subject Coefficient of Variation

agree.wscv

R Documentation

Within-subject Coefficient of Variation

Description

Obtain confidence interval and point estimate of the within-subject coefficient of variation (WSCV).

Usage

  agree.wscv(ratings, conf.level=0.95, method=c("vst", "delta"),
             NAaction=c("fail", "omit"))

Arguments

`ratings`	a matrix of observations with one subject per row and one rater per column.
`conf.level`	confidence level of the interval. The default is 0.95.
`method`	a character string specifying the method used to obtain confidence interval of the WSCV. It must be one of "vst" and "delta" and may be abbreviated. The default is "vst".
`NAaction`	a character string specifying what should happen when the data contain `NA`s. It must be one of "fail" and "omit" and may be abbreviated. The default is "fail" that causes the function to print an error message and terminate if there are any incomplete observations. If it is "omit", then the entire row(s) containing incomplete observation(s) will be deleted.

Details

The point estimate is based on what proposed in Quan and Shih (1996). To obtain confidence interval, the methods available include the delta method proposed in Quan and Shih (1996) and the variance stabilizing transformation in Shoukri et al. (2006).

Value

Point estimate of the WSCV and lower and upper bounds of the confidence interval.

References

Hui Quan and Weichung J. Shih (1996) Assessing reproducibility by the within-subject coefficient of variation with random effects models. Biometrics 52 1195-1203

Mohamed M Shoukri, Nasser Elkum and Stephen D Walter (2006) Interval estimation and optimal design for the within-subject coefficient of variation for continuous and binary variables. BMC Medical Research Methodology 6 24

Examples

  data(lesionBurden)
  agree.wscv(lesionBurden.M)