﻿ Example 8: Items with various rating scale models
 Example 8: Items with various rating scale or partial credit models

A 4 item test in which each item has a 9-level scoring rubric. We suspect that there are not really 9 levels of competence. After several Winsteps analyses, we choose to recode the rating scale or partial credit items by collapsing categories in order to increase measurement effectiveness (separation) and increase parameter stability. An objection to collapsing is that it violates the Rasch model. This is only true if the uncollapsed data strictly accord with the model. In fact, the collapsed data may fit the Rasch model better than the uncollapsed. We have to compare the collapsed and uncollapsed analyses to decide.

; This file is EXAM8.TXT

TITLE="Success and Failure Items"

NAME1=6

ITEM1=1

NI=4   ; 4 items

ISGROUPS=1234 ; one item per grouping, same as ISGROUPS=0

IREFER=ABCD  ; the 4 items are to be recoded differently. Item 1 is type "A", etc.

CODES=123456789 ; the codes in the data file

IVALUEA=333456666 ; the recoding for A-type items in IREFER=, i.e., Item 1

IVALUEB=333455555

IVALUEC=333444444

IVALUED=444456777

&END

Maze

Passengers

Blocks

Egg race

END NAMES

5536 M Richard

4545 F Tracie

4345 M Walter

3454 M Blaise

4435 M Ron

....

Table 14.3 shows the recoding:

ITEMS CATEGORY/OPTION/Distractor FREQUENCIES:  ENTRY ORDER

+------------------------------------------------------------------------+

|ENTRY   DATA  SCORE |     DATA   |     USED     AVERAGE OUTF|           |

|NUMBER  CODE  VALUE |  COUNT   % |  COUNT   %   MEASURE MNSQ|  ITEM     |

|--------------------+------------+--------------------------+-----------|

|    1   2         3 |      1   3 |      1   3     -2.39   .3|Maze       |

|        3         3 |      7  22 |      6  19     -1.57   .7|           |

|        4         4 |     10  31 |     10  32      -.54   .5|           |

|        5         5 |     10  31 |     10  32      1.23   .6|           |

|        6         6 |      3   9 |      3  10      2.42   .7|           |

|        7         6 |      1   3 |      1   3      2.78   .5|           |

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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
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