Rasch Estimation Demonstration Spreadsheet

2003. Prepared by Mark H. Moulton, Ph.D., Educational Data Systems, www.eddata.com

This Excel file was developed to help students and practitioners of the Rasch Model get a simple and intuitive look at what goes on "under the hood" of most Rasch programs for dichotomous data. The Excel workbook shows all the matrices, formulas, and iterations needed to understand how person abilities, item difficulties, standard errors, expected values, and misfit statistics are computed. It also allows the user to perform simple experiments to see the effects of missing and misfitting data. You will find that, beneath the sophistication and apparent inscrutability of modern Rasch software, the model and its estimation algorithm are surprisingly easy to understand.

The workbook most closely emulates the JMLE/UCON algorithm described by Ben Wright and Mark Stone in Best Test Design (1979).

The spreadsheet is fully documented using Excel comments, which may be turned on and off as desired.

Link to download for dichotomous spreadsheet: moulton.xls

Link to equivalent spreadsheet for polytomous (rating-scale) data: poly.xls

Available Rasch software is listed at www.rasch.org/software.htm.

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