Measuring the elements

Facets commences by reading and checking the specifications. If it finds obviously faulty specifications, omissions or contradictions it will stop and display a diagnostic message on the screen.


When the specifications are successfully processed, it writes a summary of them to the output file. The less commonly used specifications are written to the file only if a non-standard option has been selected.


Facets then locates the data, which may be at the end of the specification file following the Data= line, or in a separate file (either the standard "FACETS.DAT" or one that you have named). As each datum is read from the data file, a matching Model= specification is sought. If one is found, the combined information is written to a work file. After this input phase is completed, a report is written detailing how many data points have been matched to each model statement.

Examine the Data Summary Report carefully. Unexpected counts are diagnostic of problems in the Model= specifications or data file. Precise details of thee matching process can be obtained by specifying "Query=Y".

If Pt-biserial=Y has been specified, a pass is made through the data calculating a point-biserial correlation corresponding to each element.


Initial estimates are obtained for each element using the PROX (normal approximation algorithm) method. Simultaneously, extreme scores are flagged, and the connectedness of the element structure is examined.


Facets then attempts joint unconditional maximum likelihood estimation for all unanchored element parameters of all facets. This is an iterative procedure, and progress towards convergence is shown on the screen.


The screen displays, for each iteration, the largest marginal residual score and largest logit change for any estimate encountered so far. Only amounts larger than convergence values are displayed.


The active horizontal bar-chart (>======<) shows how far through the data Facets has progressed in that iteration. To stop iteration prematurely, press the Ctrl+"S" keys simultaneously. The bar-chart changes symbol to (>######<) to acknowledge that you have forced termination at the end of this iteration. Complete output will be produced, as though convergence has been reached.


To cancel the program immediately, press Ctrl+C keys simultaneously. Output will consist only of what Facets has already produced. This can be useful for diagnosing problems with control specifications or data file contents. Immediate cancellation can cause Facets to leave its work files behind. Files with names starting "FACETS.$$_" are not needed and can be deleted.


After convergence is achieved or termination forced, a further iteration through the data is made to calculate fit statistics and write out residual information for the responses. The element parameter estimates and summary statistics are now written to the output file.


After estimating bias interactions, if specified, Facets concludes by reporting how long it took to complete the entire analysis.

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

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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
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Coming Winsteps & Facets Events
May 22 - 24, 2018, Tues.-Thur. EALTA 2018 pre-conference workshop (Introduction to Rasch measurement using WINSTEPS and FACETS, Thomas Eckes & Frank Weiss-Motz),
May 25 - June 22, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps),
June 27 - 29, 2018, Wed.-Fri. Measurement at the Crossroads: History, philosophy and sociology of measurement, Paris, France.,
June 29 - July 27, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps),
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"
Aug. 10 - Sept. 7, 2018, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets),
Oct. 12 - Nov. 9, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps),


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