summary.rasch {ltm} | R Documentation |
Summarizes the fit of a rasch
object.
## S3 method for class 'rasch': summary(object, robust.se = FALSE, ...)
object |
an object inheriting from class rasch . |
robust.se |
logical; if TRUE robust estimation of standard errors is used, based on the sandwich estimator. |
... |
additional argument; currently none is used. |
An object of class summ.rasch
with components,
coefficients |
the estimated coefficients' table. |
Var.betas |
the approximate covariance matrix for the estimated parameters. |
logLik |
the log-likelihood of object . |
AIC |
the AIC for object . |
BIC |
the BIC for object . |
max.sc |
the maximum absolute value of the score vector at convergence. |
conv |
the convergence identifier returned by optim . |
counts |
the counts argument returned by optim . |
call |
the matched call of object . |
control |
the values used in the control argument in the fit of obj . |
nitems |
the number of items in the data set. |
For the parameters that have been constrained, the standard errors and z-values are printed as NA
.
When the coefficients' estimates are reported under the usual IRT parameterization (i.e., IRT.param = TRUE
in the call of rasch
), their standard errors are calculated using the Delta method.
Dimitris Rizopoulos dimitris.rizopoulos@med.kuleuven.be
## The Rasch model for the Wirs data, ## results are reported under the IRT ## parameterization: m <- rasch(Wirs, IRT = TRUE) summary(m) ## The Rasch model for the Lsat data, ## with the constraint that the discrimination ## parameter equals 1: m <- rasch(Lsat, constraint = cbind(6, 1)) summary(m) ## The Rasch model for the Abortion data, ## use the sandwich estimator for the standard ## errors: m <- rasch(Abortion) summary(m, TRUE)