eRm: itemfit.ppar – R documentation

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itemfit.ppar

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

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

Extended Rasch Modeling

v1.0-2

GPL-3

Authors

Patrick Mair [cre, aut], Reinhold Hatzinger [aut], Marco J. Maier [aut], Thomas Rusch [ctb], Rudolf Debelak [ctb]

Initial release

2021-02-11