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Last data update: 2014.03.03

R: Nonparametric Estimation of Conditional Covariances of Item...

ccov.np

R Documentation

Nonparametric Estimation of Conditional Covariances of Item Pairs

Description

This function estimates conditional covariances of itempairs (Stout, Habing, Douglas & Kim, 1996; Zhang & Stout, 1999a). The function is used for the estimation of the DETECT index.

Usage

ccov.np(data, score, bwscale = 1.1, thetagrid = seq(-3, 3, len = 200), 
    progress = TRUE)

Arguments

`data`	An N \times I data frame of dichotomous responses. Missing responses are allowed.
`score`	An ability estimate, e.g. the WLE
`bwscale`	Bandwidth factor for calculation of conditional covariance. The bandwidth used in the estimation is `bwscale` times N^{-1/5}.
`thetagrid`	A vector which contains theta values where conditional covariances are evaluated.
`progress`	Display progress?

Note

This function is used in conf.detect and expl.detect.

Author(s)

Alexander Robitzsch

References

Stout, W., Habing, B., Douglas, J., & Kim, H. R. (1996). Conditional covariance-based nonparametric multidimensionality assessment. Applied Psychological Measurement, 20, 331-354.

Zhang, J., & Stout, W. (1999). Conditional covariance structure of generalized compensatory multidimensional items, Psychometrika, 64, 129-152.