isop.test {sirt} | R Documentation |
Testing the ISOP Model
Description
This function performs tests of the W1 axiom of the ISOP model
(Scheiblechner, 2003). Standard errors of the corresponding statistics
are obtained by Jackknife.
Usage
isop.test(data, jackunits=20, weights=rep(1, nrow(data)))
## S3 method for class 'isop.test'
summary(object,...)
Arguments
data |
Data frame with item responses |
jackunits |
A number of Jackknife units (if an integer is provided as the argument value) or a vector in the Jackknife units are already defined. |
weights |
Optional vector of sampling weights |
object |
Object of class |
... |
Further arguments to be passed |
Value
A list with following entries
itemstat |
Data frame with test and item statistics for the W1 axiom.
The |
Es |
Number of concordances per item |
Ed |
Number of disconcordances per item |
The statistics are printed by the
summary
method.
References
Scheiblechner, H. (2003). Nonparametric IRT: Testing the bi-isotonicity of isotonic probabilistic models (ISOP). Psychometrika, 68, 79-96.
See Also
Fit the ISOP model with isop.dich
or isop.poly
.
See also the ISOP package at Rforge: http://www.rforge.net/ISOP/.
Examples
#############################################################################
# EXAMPLE 1: ISOP model data.Students
#############################################################################
data(data.Students, package="CDM")
dat <- data.Students[, paste0("act",1:5) ]
dat <- dat[1:300, ] # select first 300 students
# perform the ISOP test
mod <- sirt::isop.test(dat)
summary(mod)
## -> W1i statistics
## parm N M est se t
## 1 test 300 NA 0.430 0.036 11.869
## 2 act1 278 0.601 0.451 0.048 9.384
## 3 act2 275 0.473 0.473 0.035 13.571
## 4 act3 274 0.277 0.352 0.098 3.596
## 5 act4 291 1.320 0.381 0.054 7.103
## 6 act5 276 0.460 0.475 0.042 11.184