Description Usage Arguments Details Value Note Author(s) References See Also Examples

plots diagnostic graphs for items flagged for DIF

1 2 |

`x` |
output from |

`labels` |
labels for group levels, e.g., c("Male","Female") |

`width` |
width of the canvas of the plotting device in inches |

`height` |
height of the canvas of the plotting device in inches |

`...` |
extra graphical parameters |

Generates the following graphs IF there is one or more DIF items: 1. Trait Distributions - density graphs for groups 2. Item True Score Functions - true score functions by theta for groups 3. Differences in Item True Score Functions - unsigned differences 4. Item Response Functions - item response function for groups 5. Impact (Weighted by Density) - unsigned differences weighted by theta distributions for the focal group 6. Comparison of TCCs by group based on all items and DIF items 7. Impact on Theta Estimates - theta estimates by group before and after accounting for DIF

Graphs 2-5 are generated for each DIF item Graphs 1, 6 and 7 are generated for the whole analysis

Returns no object.

Produces graphs only if x contains DIF items. No graphs if no DIF items are present.

Seung W. Choi <[email protected]>

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/.

1 2 3 | ```
##run lordif first
## Not run: age.dif <- lordif(Anxiety[paste("R",1:29,sep="")],Anxiety$age)
## Not run: plot(age.dif,labels=c("Younger","Older"),width=8,height=7,cex=0.8,lwd=1)
``` |

```
Loading required package: mirt
Loading required package: stats4
Loading required package: lattice
Loading required package: rms
Loading required package: Hmisc
Loading required package: survival
Loading required package: Formula
Loading required package: ggplot2
Attaching package: 'Hmisc'
The following objects are masked from 'package:base':
format.pval, units
Loading required package: SparseM
Attaching package: 'SparseM'
The following object is masked from 'package:base':
backsolve
```

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