Rasch Analysis

Rasch analysis can be applied to assessments in a wide range of disciplines, including health studies, education, psychology, marketing, economics and social sciences.

Many assessments in these disciplines involve a well defined group of people responding to a set of items for assessment. Generally, the responses to the items are scored 0, 1 (for two ordered categories); or 0, 1, 2 (for three ordered categories); or 0, 1, 2, 3 (for four ordered categories) and so on, to indicate increasing levels of a response on some variable such as health status or academic achievement. These responses are then added across items to give each person a total score. This total score summarise the responses to all the items, and a person with a higher total score than another one is deemed to show more of the variable assessed. Summing the scores of the items to give a single score for a person implies that the items are intended to measure a single variable, often referred to as a unidimensional variable.

The Rasch model is the only item response theory (IRT) model in which the total score across items characterizes a person totally. It is also the simplest of such models having the minimum of parameters for the person (just one), and just one parameter corresponding to each category of an item. This item parameter is generically referred to as a threshold. There is just one in the case of a dichotomous item, two in the case of three ordered categories, and so on.

1. What is Rasch Analysis

2. Why undertake a Rasch analysis?

3. The research paradigm and the Rasch model

4. Is there more than one Rasch model?

5. Different Rasch Model Specifications

6. Thresholds and Steps

7. Disordered Thresholds as an Anomaly

8. Who should use a Rasch analysis?

9. An ideal approach to a Rasch analysis?

10. Recommended Rasch Software

11. The RUMM approach to Rasch Analysis

12. Courses and Workshops available on Rasch Analysis

Introduction to Rasch Measurement and Traditional Test Theory
Internet based course on Rasch Analysis beginning from first principles it introduces the Guttman stucture as a lead into both traditional test theory and Rasch measurement. The Course reviews elementary traditional test theory in a way that it relates to the Rasch models and the necessary elementary statistics as well as the dichotomous model and the model for ordered response categories. Model fit including differential item functioning is also covered. A feature of the course is a discussion group which permits you to interact with other students in the class. Students are also provided with a full version of the interactive Windows program RUMM for analysing data during the semester.

Psychometric Laboratory for Health Sciences
A workshop to introduce Rasch analysis. It will suit those working in the measurement of outcomes in the health sciences, of attitudinal data in the social sciences, or in educational testing. It will take the form of hands-on tuition in using the Rasch Unidimensional Measurement Models (RUMM2030) software package. At the end of the two-and-a-half days workshop students should understand and be able to analyse data, using RUMM2030, for: