ItemFit function

Compute item fit statistics for outputs generated by estimation functions in the package

This function computes item fit statistics for outputs generated by estimation functions in the package, including AlphaNP, AlphaMLE, ParMLE, andJMLE. The function currently provides the RMSEA and Chi-square item fit statistics.

ItemFit(x, model=NULL, par=NULL)

Arguments

• x: The output from the function (The list of all outputs).
• model: This needs to be additionally specified only when x is output from AlphaNP. Currently support five models: "DINA", "DINO", "NIDA", "GNIDA", and "RRUM".
• par: This needs to be additionally specified only when x is output from AlphaNP. A list of parameters. DINA & DINO --- par$slip: a vector of slipping parameters for each item; par$guess: a vector of guessing parameters for each item. NIDA --- par$slip: a vector of slipping parameters for each attribute; par$guess: a vector of guessing parameters for each attribute. GNIDA --- par$slip: a matrix (items by attributes) of slipping parameters; par$guess: a matrix (items by attributes) of guessing parameters. RRUM --- par$pi: a vector of pi parameters for each item; par$r: a matrix (items by attributes) of r parameters.

Returns

• RMSEA: The model-based root mean square error of approximation (Kunina-Habenicht et al., 2012) of each item based on the estimated or given item parameter, Q-vector, and alpha matrix.

• Chisq: The Q1 Chi-square statistic (Wang et al., 2015; Yen, 1981) of each item based on the estimated or given item parameter, Q-vector, and alpha matrix.

• Chisq.p: The p-values for the Chi-square statistic for each item.

• Chisq.df: The degrees of freedom for the Chi-square statistic for each item.

See Also

AlphaNP, AlphaMLE, ParMLE, JMLE

References

Kunina-Habenicht, O., Rupp, A. A., & Wilhelm, O. (2012). The Impact of Model Misspecification on Parameter Estimation and Item-Fit Assessment in Log0Linear Diagnostic Classification Models. Journal of Educational Measurement, 49(1), 59-81.

Wang, C., Shu, Z., Shagn, Z., & Xu, G. (2015). Assessing Item-Level Fit for the DINA Model. Applied Psychological Measurement, 1-14.

Yen, W. M. (1981). Using Simulation Results to Choose a Latent Trait Model. Applied Psychological Measurement, 5, 245-262.

Examples

# See examples in AlphaNP, AlphaMLE, ParMLE, and JMLE.