# 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

## Cloud Rasch Analysis Engine & APIs

Rumlab and Timewatch have developed a cloud based rasch analysis engine and APIs which allow anyone to take full advantage of the power of the Rasch engine, with out the need to understand or implement the complex mathematics involved.

The system allows for data and test instrument setup data (created via Rumm2030 or any other means) to be transmitted securely via SSL to a cloud server, with resultant data securely returned. The cloud servers do store customer setup data, test or result data, and we recommend that data passed to the servers be anonymous or utilize random reference id's so that only the entity calling the service can interpret the meaning of the data and the result.

### Rasch Analysis API's

Although the Rasch Cloud Server can provide a test page for customers to upload their test instrument data (item's, item labels, thresholds etc.), this is provided to demonstrate how with purely instrument data a fully responsive web application that can support PCs, Macs, Phones and Tablets in portrait or landscape mode can support real time testing and demonstrate the speed and versatility of the Rasch Analysis engine as resultant data is displayed on the test page. The intention is that developers that wish to create their own Test or Questionnaire sustems can do so, but can securely utlize our Rash Analysis API's to analyze their data and provide resultant test scores.

## RUMM Software

The RUMM2030 program has been developed with the Rasch paradigm and with the case-study approach to a Rasch analysis. It is used interactively to move between many different graphic displays and corresponding statistics in making decisions.

Thus RUMM2030 places the researcher in dynamic and interactive control in being able to look at complementary evidence in making a decision.

The RUMM2030 program has been written to permit the researcher to study relevant graphs and statistical tables. The easy interactive moving between statistics and graphs also makes RUMM2030 an ideal tool for teaching and learning about the Rasch model.

For example, RUMM2030 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 parameterization), or different across items (partial credit parameterization).

The RUMM2030 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 items), test equating (providing equivalent test scores between tests of different sub sets of items), assessment of dimensionality, assessment of local response dependence, conditional test-of-fit (for a pair of polytomous items or a pair of tests), tailored test analysis (for testing the significance of guessing), facet analysis (for up to 3-way item response structure), principal component analyses of residuals, and tests specifically regarding the profiles of individuals.
• 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 items which show between group DIF, RUMM2030 provides a simple facility to split items routinely 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 the full range of data tables and graphics. " Facility to copy and paste easily all, or part, of the data table displays to spreadsheets (e.g EXCEL or SPSS) for additional analyses.

RUMM2030 comes complete with

• Manuals: to assist both the beginner and experienced researcher.
• Interpretation Guides: up to seven Interpreting the RUMM2030 Analysis monographs, providing a detailed guide on how to employ the RUMM paradigm in the conduct of any Rasch analysis.

One testimonial describes the Interpreting RUMM2030 publication as "…the best documentation for any Rasch program by a long shot. Excellent writing and well explained".

RUMM2030 is suggested for

• a researcher wanting to conduct an item analysis leading to the construction of a meaningful variable suitable for providing consistent measurement, or
• a teacher seeking a user-friendly computer application for instructing students in the good conduct of item analyses, then the RUMM2030 program should be a great help to you. The ease of use means that RUMM2030 is a great time saver as it does not involve any stop-start requirements associated with the preparation of batch files before moving on to the next procedure or display.

However, once specifications are read in, RUMM2030 does save batch files (called templates), and with large data sets, batch files/templates which specify the format of the data and which specify the scoring of the responses can be constructed readily and imported interactively. It must be emphasized here that the RUMM2030 batch files/templates are aids, or tools, for creating a new analysis setup (such as anchoring) and, once created and implemented, the employment of the RUMM paradigm in the conduct of the subsequent Rasch analysis within RUMM2030 can proceed as normal, that is, no batch files are required in the conduct and diagnostic interpretations of the analysis are involved.

11. The RUMM approach to Rasch Analysis

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

13. What cloud analysis engines and API's are available?

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