plot method for pairwise DIF statistics

# S3 method for DIF_stats
plot(x, items = NULL, itemsX = items, itemsY = items, alpha = 0.05, ...)

## Arguments

x

object produced by DIF

items

character vector of item id's for a subset of the plot. Useful if you have many items. If NULL all items are plotted.

itemsX

character vector of item id's for the X axis

itemsY

character vector of item id's for the Y axis

alpha

significance level used to color the plot (two sided)

...

further arguments to plot

## Details

Plotting produces an image of the matrix of pairwise DIF statistics. The statistics are standard normal deviates and colored to distinguish significant from non-significant values. If there is no DIF, a proportion alpha off the cells will be colored significant by chance alone.

## References

Feskens, R., Fox, J. P., & Zwitser, R. (2019). Differential item functioning in PISA due to mode effects. In Theoretical and Practical Advances in Computer-based Educational Measurement (pp. 231-247). Springer, Cham.