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.

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

The RUMM2020 program has been developed with the Rasch paradigm and with the case study conceptualization of a Rasch analysis. It is used interactively to move between many different graphics and corresponding statistics in making decisions.

Thus RUMM2020 places the researcher in dynamic and interactive control in being able to look at complementary evidence in making a decision.

The RUMM2020 program has been written to permit the researcher to look carefully at graphs and statistical tables. The easy interactive moving between statistics and graphs also makes RUMM2020 it an ideal tool for teaching and learning about the Rasch model.

For example, RUMM2020 makes possible, using a simple selection option, to analyze items with more than two categories as either hypothesizing the same thresholds across items (rating scale), or different across items (partial credit).

The RUMM2020 program has the following features characteristic of a full Windows application:

The use of standard tools and objects familiar to any Windows operator.
A simple visual structure for data input and item specifications.
Easy creation and importing of templates for involved and elaborate analyses.
User friendly and efficient displays for analyzing data according to the Rasch paradigm.
Extensive use of elaborate graphics to both complement and extend the meaning of the different parameter estimates and fit statistics.
A range of advanced extensions involving item rescoring, DIF, subtests (for assessing local independence in items), anchoring strategies, distractor analysis (for multiple choice data), test equating (providing equivalent test scores between tests of different sub sets of items), principal component displays (for person test-of-fit residuals).
The DIF diagnostic is an advanced and comprehensive routine for not only identifying DIF but also for accounting for the DIF. Instead of resorting to deleting such items, RUMM2020 provides a simple facility to routinely split items to account for the DIF.
Comprehensive tools for editing specification labels and graphic-based labels; displaying and recovering to files the original response data file and test specifications; saving to file and sending direct to the printer the full range of data tables and graphics.
Facility to easily copy and paste all or part of the data table displays to spreadsheets (e.g EXCEL or SPSS) for additional analyses.

11. Examples of Rasch analyses involve RUMM2020

12. What courses and workshops are available on Rasch analysis?