ccov.np: 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?
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.