﻿ Introduction

# Introduction

Facets is Windows-based software which assists in many applications of the Rasch model, particularly in the areas of performance assessment and paired comparisons. We recommend that you first become familiar with the conceptually and operationally simpler Rasch-measurement program WINSTEPS before embarking on Facets. We also offer Training Courses - please contact us for details. There is more information at: www.winsteps.com

This manual contains instructions for operating Facets, a computer program for the construction of linear measures from qualitatively-ordered counts by means of many-facet Rasch analysis. The theory underlying the program is described in reference MFRM. These instructions also apply to MINIFAC, the student/evaluation version of Facets, which has exactly the same functionality, but is limited in the number of observations it can analyze.

A basic many-facet Rasch model for observation Xnmij is:

log ( Pnmijk / Pnmij(k-1) ) = Bn - Am - Di - Cj - Fk

where

Bn is the ability of person n, e.g., examinee: Mary,

Am is the challenge of task m, e.g., an essay: "My day at the zoo",

Di is the difficulty of item i, e.g., punctuation,

Cj is the severity of judge j, e.g., the grader: Dr. Smith,

Fk is the barrier to being observed in category k relative to category k-1.

Pnmijk is the probability of category k being observed.

Pnmij(k-1) is the probability of category k-1 being observed.

Persons, tasks, items and judges are facets. The elements include Mary, "My day at the zoo", punctuation, and Dr. Smith. For each element, Facets provides a measure (linear quantity), its standard error (precision) and five fit statistics (statistical validity). The fit statistics enable diagnosis of aberrant observations and idiosyncratic elements. Facets also provides calibrations of response format structures, such as rating scales, partial credit items, letter grades and ranks. Results are presented in tables and graphically. The graphical presentation of measures is in a "ruler" format especially useful to non-technical users.

Facets can also quantify discrepant interactions between elements of different facets. Once measures have been estimated from a data set, differential facet functioning, equivalent to differential item functioning or "item bias", can be investigated automatically. A judge's bias on one item, or an item's bias against a group of persons can be identified and its size and statistical significance estimated.

Facets is ideally suited for essay grading, portfolio assessment and other kinds of judged performances. Its use is not limited to educational and psychological testing. It is employed to convert qualitative observations to linear measures in many areas of research and practice, including product development, sports science, pollution control, public speaking and the arts.

See References.

We acknowledge the kind permission granted by Chris Hanscom of Veign for the use of their Jeweled Style Command Button.

Help for Facets Rasch Measurement Software: www.winsteps.com Author: John Michael Linacre.

 Forum Rasch Measurement Forum to discuss any Rasch-related topic

Rasch Publications
Rasch Measurement Transactions (free, online) Rasch Measurement research papers (free, online) Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch Applying the Rasch Model 3rd. Ed., Bond & Fox Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement with Raters and Rating Scales: Rasch Models for Rater-Mediated Assessments, George Engelhard, Jr. & Stefanie Wind Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement Rasch models for measurement, David Andrich Constructing Measures, Mark Wilson Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish: Análisis de Rasch para todos, Agustín Tristán Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez
Winsteps Tutorials Facets Tutorials Rasch Discussion Groups

Coming Rasch-related Events
Jan. 5 - Feb. 2, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
Jan. 10-16, 2018, Wed.-Tues. In-person workshop: Advanced Course in Rasch Measurement Theory and the application of RUMM2030, Perth, Australia (D. Andrich), Announcement
Jan. 17-19, 2018, Wed.-Fri. Rasch Conference: Seventh International Conference on Probabilistic Models for Measurement, Matilda Bay Club, Perth, Australia, Website
Jan. 22-24, 2018, Mon-Wed. In-person workshop: Rasch Measurement for Everybody en español (A. Tristan, Winsteps), San Luis Potosi, Mexico. www.ieia.com.mx
April 10-12, 2018, Tues.-Thurs. Rasch Conference: IOMW, New York, NY, www.iomw.org
April 13-17, 2018, Fri.-Tues. AERA, New York, NY, www.aera.net
May 22 - 24, 2018, Tues.-Thur. EALTA 2018 pre-conference workshop (Introduction to Rasch measurement using WINSTEPS and FACETS, Thomas Eckes & Frank Weiss-Motz), https://ealta2018.testdaf.de
May 25 - June 22, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
June 27 - 29, 2018, Wed.-Fri. Measurement at the Crossroads: History, philosophy and sociology of measurement, Paris, France., https://measurement2018.sciencesconf.org
June 29 - July 27, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps), www.statistics.com
July 25 - July 27, 2018, Wed.-Fri. Pacific-Rim Objective Measurement Symposium (PROMS), (Preconference workshops July 23-24, 2018) Fudan University, Shanghai, China "Applying Rasch Measurement in Language Assessment and across the Human Sciences" www.promsociety.org
Aug. 10 - Sept. 7, 2018, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com
Sept. 3 - 6, 2018, Mon.-Thurs. IMEKO World Congress, Belfast, Northern Ireland www.imeko2018.org
Oct. 12 - Nov. 9, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com

Our current URL is www.winsteps.com