Rasch hour time, dear fellow slatisticians! Yes, we need to Rasch! Rasch analysis is a statistical method used for estimating the probability of success of particular persons on particular items. These probabilities are expressed in logits. The Rasch models can be applied to a wide range of data types. The Rasch family consists of the simple Rasch model (can only be used to analyze dichotomous data such as right or wrong), the rating scale model (handles data with rating scales such as likert-scale items), the partial credit model (in a writing or speaking test) and the many-facet Rasch model (suitable for analyzing multiple aspects of testing such as the test location, the experience of raters and so on). Some of the modern software packages used for Rasch models are Winsteps, Facets, RUMM, and Conquest. Probably one of the most useful output from a Rasch analysis is item/person map (aka Wright Map). This map (see the figure above) provides a vertical histogram describing the representation of persons and items on the same measurement scale. The Rasch models are slowly finding their way into L2 research. I am planning to use a Rasch model for my dissertation. I will update this post as I learn something new about the Rasch family…stay tuned!

Further reading:

Knoch, U., & McNamara, T. (2015). Rasch analysis. In L. Plonsky (Ed.), Advancing quantitative methods in second language research (pp. 275-304). New York: Routledge.