eRm (version 0.15-6)

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.

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, ...)
## 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.

...

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).
• 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).

encoding

UTF-8

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.84-5

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)