Runs ordinal logistic regression models and produces DIF statistics and effect size measures
runolr(rv, ev, gr, wt)Returns a list of the following components:
prob for the LR Chi-square comparing Model 1 vs. Model 2
prob for the LR Chi-square comparing Model 1 vs. Model 3
prob for the LR Chi-square comparing Model 2 vs. Model 3
proportional change in the coefficient for ev
Cox & Snell psudo R-square for Model 1
Cox & Snell psudo R-square for Model 2
Cox & Snell psudo R-square for Model 1
Nagelkerke psudo R-square for Model 1
Nagelkerke psudo R-square for Model 2
Nagelkerke psudo R-square for Model 3
McFadden psudo R-square for Model 1
McFadden psudo R-square for Model 2
McFadden psudo R-square for Model 3
Cox & Snell R-square change from Model 1 to Model 2
Cox & Snell R-square change from Model 1 to Model 3
Cox & Snell R-square change from Model 2 to Model 3
Nagelkerke R-square change from Model 1 to Model 2
Nagelkerke R-square change from Model 1 to Model 3
Nagelkerke R-square change from Model 2 to Model 3
McFadden R-square change from Model 1 to Model 2
McFadden R-square change from Model 1 to Model 3
McFadden R-square change from Model 2 to Model 3
df for the LR Chi-square comparing Model 1 and Model 2
df for the LR Chi-square comparing Model 1 and Model 3
df for the LR Chi-square comparing Model 2 and Model 3
a response variable
an explanatory variable (e.g., conditioning variable)
a vector of group identifiers
a vector of optional sample weights
Seung W. Choi <choi.phd@gmail.com>
Model 1: ev
Model 2: ev + gr
Model 3: ev*gr or equivalently ev + gr + ev*gr
Choi, S. W., Gibbons, L. E., Crane, P. K. (2011). lordif: An R Package for Detecting Differential Item Functioning Using Iterative Hybrid Ordinal Logistic Regression/Item Response Theory and Monte Carlo Simulations. Journal of Statistical Software, 39(8), 1-30. URL http://www.jstatsoft.org/v39/i08/.
Crane, P. K., Gibbons, L. E., Jolley, L., & van Belle, G. (2006). Differential item functioning analysis with ordinal logistic regression techniques: DIF detect and difwithpar. Medical Care, 44(11 Suppl 3), S115-S123.
rundif, lordif, rms