3 facet dichotomy with item bias: The Knox Cube Test
In a standard two-facet Knox Cube analysis, respondent gender (sex) is indicated, but item bias (DIF, differential item functioning) is not computed. Here we add a DIF detection by coding a dummy "gender" Facet.
The Knox Cube Test measures short term memory (BTD p.28). There are two facets, Children and Tapping Items. Observations are scored as dichotomies, 1 for correct and 0 for incorrect.
Facets specifications and data (in file Kcta.txt):
Title = Knox Cube Test (Best Test Design p.31) ; the report heading line
Facets = 3 ; three facets: children and items and gender
Positive = 1 ; for facet 1, children, higher score = higher measure
Noncenter = 1 ; only facet 1, children, does not have mean measure set to zero
Pt-biserial = Yes ; report the point-biserial correlation
Vertical = 1*,1A,2N,2A ; show children by distribution and sex, taps by number and name
Yard = 112,4 ; Vertical rulers 112 columns wide, with 4 lines per logit
Model = ?,?B,?B,D ; look for bias/interaction between 2nd and 3rd Facets
1,Children ; Children are facet 1
1-17 = Boy,,1 ; Pretend boys, in group 1, are numbered 1 through 17.
18-35 = Girl,,2 ; Pretend girls, in group 2, are numbered 18 through 35.
* ; end of child labels for facet 1
2,Tapping items ; Items are facet 2
1 = 1-4 ; Items labelled by the order in which the four blocks are tapped
2 = 2-3
3 = 1-2-4
4 = 1-3-4
5 = 2-1-4
6 = 3-4-1
7 = 1-4-3-2
8 = 1-4-2-3
9 = 1-3-2-4
3,Gender,A ; Dummy gender facet is anchored
1=boys,0 ; anchor at 0 so do not affect analysis
2=girls,0 ; anchor at 0 so do not affect analysis
* ; end of item labels
Data = ; no data file name, so data follows immediately in this file
1,1,1, 1 ; child 1 on item 1 is a boy scored 1 (blanks are ignored)
1,2-18,1, 1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0 ; child 1 on item 2 is a boy scored 1, on item 3 scored 1, etc to item 18
| ; 594 more observations, 18 per data line
35,1-18,2, 1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ; child 35, a girl, scored 1 on items 1-3, 0 on items 4-18
Here is the DIF report:
The reported DIF is against the overall item difficulty. The boys vs. girls DIF size on item 4, tapping pattern 1-3-4, is:
DIF size = Target Contrast Target measure for boys - Target measure for girls = -.4.47 - -4.08 = -.41.
We can see by comparing the observed and expected scores, that the boys scored 15 when 14.8 was expected, and the girls 17 when 17.1 was expected. So the item was .41 logits easier for the boys than for the girls. The t-test for this DIF size is approximately DIF size / joint standard error: t = -.41 / sqrt(SE(boy)² + SE(girl)²) = -.41/ sqrt(1.17²+1.11²) = .43/1.61 = -.25 with (boys count - 1 + girls count - 1) = 32 degrees of freedom. P=.80 for a 2-sided t-test. So this is not statistically significant. The hypothesis of "No DIF" is not rejected.
Help for Facets Rasch Measurement Software: www.winsteps.com Author: John Michael Linacre.
For more information, contact firstname.lastname@example.org or use the Contact Form
|Facets Rasch measurement software.
Buy for $149. & site licenses.
Freeware student/evaluation download
Winsteps Rasch measurement software. Buy for $149. & site licenses. Freeware student/evaluation download
|State-of-the-art : single-user and site licenses : free student/evaluation versions : download immediately : instructional PDFs : user forum : assistance by email : bugs fixed fast : free update eligibility : backwards compatible : money back if not satisfied|
Rasch, Winsteps, Facets online Tutorials
|Forum||Rasch Measurement Forum to discuss any Rasch-related topic|
Click here to add your email address to the Winsteps and Facets email list for notifications.
Click here to ask a question or make a suggestion about Winsteps and Facets software.
|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
Winsteps® is a registered trademark
|Concerned about aches, pains, youthfulness? Mike and Jenny suggest Liquid Biocell|