itemfit.ppar: Residuals, Personfit and Itemfit Statistics

In eRm: Extended Rasch Modeling

Residuals, Personfit and Itemfit Statistics

Description

pmat computes the theoretical person-item matrix with solving probabilities for each category (except 0th). residuals computes the squared and standardized residuals based on the observed and the expected person-item matrix. Chi-square based itemfit and personfit statistics can be obtained by using itemfit and personfit. Corrected item-test correlations in itemfit are computed using the approach from Cureton (1966).

Usage

## S3 method for class 'ppar'
pmat(object)
## S3 method for class 'ppar'
residuals(object,...)
## S3 method for class 'ppar'
itemfit(object)
## S3 method for class 'ppar'
personfit(object)
## S3 method for class 'ifit'
print(x, visible = TRUE, 
sort_by = c("none", "p", "outfit_MSQ", "infit_MSQ", "outfit_t", "infit_t", "discrim"), 
decreasing = FALSE, digits = 3,...)
## S3 method for class 'pfit'
print(x, visible = TRUE, ...)
## S3 method for class 'resid'
print(x, ...)

Arguments

object	Object of class ppar, derived from person.parameter.
x	Object of class ifit, pfit, or resid.
visible	If FALSE, returns the matrix of fit statistics that otherwise would be printed.
sort_by	Optionally the itemfit output can be sorted by one of these criteria.
decreasing	If sort_by is set, whether the output should be sorted in increasing or decreasing order.
digits	How many digits should be printed.
...	Further arguments passed to or from other methods. They are ignored in this function.

Value

pmat	Matrix of theoretical probabilities for each category except 0th (from function pmat).
i.fit	Chi-squared itemfit statistics (from function itemfit).
i.df	Degrees of freedom for itemfit statistics (from function itemfit).
st.res	Standardized residuals (from function itemfit).
i.outfitMSQ	Outfit mean-square statistics (from function itemfit).
i.infitMSQ	Infit mean-square statistics (from function itemfit).
i.disc	Corrected item-test correlations (from function itemfit).
p.fit	Chi-squared personfit statistics (from function personfit).
p.df	Degrees of freedom for personfit statistics (from function personfit).
st.res	Standardized residuals (from function personfit).
p.outfitMSQ	Outfit mean-square statistics (from function personfit).
p.infitMSQ	Infit mean-square statistics (from function personfit).

Author(s)

Patrick Mair, Reinhold Hatzinger, Moritz Heene

References

Smith Jr., E. V., and Smith, R. M. (2004). Introduction to Rasch Measurement. JAM press.

Wright, B.D., and Masters, G.N. Computation of OUTFIT and INFIT Statistics. Rasch Measurement Transactions, 1990, 3:4 p.84-85

Cureton, E. E. (1966). Corrected item-test correlations. Psychometrika, 31, 93-96

See Also

person.parameter

Examples

# Rasch model, estimation of item and person parameters
res <- RM(raschdat2)
p.res <- person.parameter(res)

# Matrix with expected probabilities and corresponding residuals
pmat(p.res)
residuals(p.res)

#Itemfit
itemfit(p.res)

#Personfit
personfit(p.res)

eRm documentation built on May 29, 2024, 2:12 a.m.