GoF.rasch {ltm} | R Documentation |
Performs a parametric Bootstrap test for Rasch models.
GoF.rasch(object, B = 49, ...)
object |
an object inheriting from class rasch . |
B |
the number of Bootstrap samples. See Details section for more info. |
... |
additional arguments; currently none is used. |
GoF.rasch
performs a parametric Bootstrap test based on Pearson's chi-squared statistic defined as
sum_{r=1}^{2^p} (O_r - E_r)^2 / E_r,
where r represents a response pattern, O_r and E_r represent the observed and expected frequencies, respectively and p denotes the number of items. The Bootstrap approximation to the reference distribution is preferable compared with the ordinary Chi-squared approximation since the latter is not valid especially for large number of items (=> many response patterns with expected frequencies smaller than 1).
In particular, the Bootstrap test is implemented as follows:
object
compute the observed value of the statistic T_{obs}.B
times and estimate the p-value using
[1 + {# T_i > T_{obs}}]/(B + 1).
An object of class GoF.rasch
with components,
Tobs |
the value of the Pearson's chi-squared statistic for the observed data. |
B |
the B argument specifying the number of Bootstrap samples used. |
call |
the matched call of object . |
p.value |
the p-value of the test. |
Dimitris Rizopoulos dimitris.rizopoulos@med.kuleuven.be
person.fit
,
item.fit
,
margins
,
rasch
## GoF for the Rasch model for the LSAT data: fit <- rasch(LSAT) GoF.rasch(fit)