MODELS= assigns model types to items = R, dichotomy, rating or partial credit scale
Winsteps chooses the model-family based on MODELS=
Models=R (or MODELS= is omitted) is the rating-scale family of models which includes the Andrich Rating-Scale Model, the Masters Partial-Credit Model, the Grouped Rating-Scale Model and the Rasch Dichotomous Model.
MODELS= *file name
file containing details
MODELS = *
MODELS = codes
codes for item groups
Within Models=R, the choice of model is decided by ISGROUPS=
If ISGROUPS= is omitted, then
1) If there are only two categories in the data the dichotomous model
2) If there are more than two categories the Andrich Rating-Scale Model
If ISGROUPS=0 then
the Masters Partial Credit Model
If ISGROUPS=(something else)
the Grouped Rating-Scale Model
Please look at the output in Table 3.2, 3.3, .... to see exactly how the data have been modeled.
Winsteps estimates calibrations for four different ordered response category structures. Dichotomies are always analyzed using the Rasch dichotomous model, regardless of what model is specified for polytomies. Items are assigned to the model for which the serial location in the MODELS= string matches the item sequence number.
The item grouping default becomes the "Partial Credit Model' each item with its own rating scale: MODEL=R and ISGROUPS=0.
Do not specify MODELS= unless you intend to use the "S" or "F" models.
MODELS=R (standard) is the default option, specifying standard Rasch analyses using the Rasch dichotomous model, Andrich "Rating Scale" model and Masters' "Partial Credit" model, see ISGROUPS=.
Andrich D. (1978) A rating scale formulation for ordered response categories. Psychometrika, 43, 561-573.
Masters G.N. (1982) A Rasch model for partial credit scoring. Psychometrika, 47, 149-174.
MODELS=S uses the Rasch dichotomous model and the Glas-Verhelst "Success" (growth) model, also called the "Steps" Model (Verhelst, Glas, de Vries, 1997). If and only if the person succeeds on the first category, another category is offered until the person fails, or the categories are exhausted, e.g. an arithmetic item, on which a person is first rated on success on addition, then, if successful, on multiplication, then, if successful, on division etc. "Scaffolded" items can function this way. This is a continuation ratio model parameterized as a Rasch model with missing data on unreached categories. Verhelst N.D., Glas C.A.W. & De Vries H.H. (1997) A Steps model to analyze partial credit. In W.J. van der Linden & R.K. Hambleton (Eds.), Handbook of modern item response theory (pp. 123 - 138) New York: Springer.
Recommendation: Instead of an S-type polytomy, model each step to be a dichotomy: 1=succeeded, 0=failed, missing=not reached. This facilitates much more powerful diagnosis of the functioning of the success process.
MODELS=F uses the Rasch dichotomous model and the Linacre "Failure" (mastery) model. If a person succeeds on the first category, top rating is given and no further categories are offered. On failure, the next lower category is administered until success is achieved, or categories are exhausted. This is a continuation ratio model parameterized as a Rasch model with missing data on unreached categories. The Success and Failure model computations were revised at Winsteps version 3.36, August 2002.
Recommendation: Instead of an F-type polytomy, model each step to be a dichotomy: 1=succeeded, 0=failed, missing=not reached. This facilitates much more powerful diagnosis of the functioning of the failure process.
MODELS= has three forms: MODELS=RRSSFR and MODELS=* list * and MODELS=*filename. When only one letter is specified with MODELS=, e.g., MODELS=R, all items are analyzed using that model. Otherwise MODELS=some combination of R's, F's, S's, and G's, e.g., MODELS=RRSF
When XWIDE=2 or more, then
either (a) Use one character per XWIDE and blanks,
MODELS=' R S R F R S R R' ; this also forces ISGROUPS=0 to be the default
or (b) Use one character per item with no blanks
RESCORE='RSRFRSRR' ; this also forces ISGROUPS=0 to be the default
Example 1: All items are to be modeled with the "Success" model.
MODELS=S ; the Success model
Example 2: A competency test consists of 3 success items followed by 2 failure items and then 10 dichotomies. The dichotomies are to be reported as one grouping.
NI=15 fifteen items
MODELS=SSSFFRRRRRRRRRR ; matching models: ; forces ISGROUPS=0 to be the default
ISGROUPS=000001111111111 ; dichotomies grouped: overriding the default ISGROUPS=0
Help for Winsteps Rasch Measurement Software: www.winsteps.com. Author: John Michael Linacre
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|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|
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