eRm (version 1.0-6)

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 ppar
pmat(object)
# S3 method for ppar
residuals(object,...)
# S3 method for ppar
itemfit(object)
# S3 method for ppar
personfit(object)
# S3 method for 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 pfit
print(x, visible = TRUE, ...)
# S3 method for resid
print(x, ...)

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).

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.

Author

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)