Table 31.3 Differential person functioning DPF list
Top Up Down
Table 31 supports the investigation of item bias, Differential Person Functioning (DPF), i.e., interactions between individual persons types of items. Specify DPF= for item classifying indicators in item labels. Person bias and DPF are the same thing.
You want to examine person bias (DPF) between starting-blocks in Exam1.txt. You need a column in your Winsteps item label that has two (or more) item type codes.
DPF class specification is: DPF=$S1W2
| TAP OBSERVATIONS BASELINE DPF DPF DPF DPF DPF KID |
| CLASS COUNT AVERAGE EXPECT MEASURE SCORE MEASURE SIZE S.E. t Prob. Number Name |
| 1- 11 .18 .23 -2.94 -.05 -3.52 -.58 1.05 -.55 .5937 1 Adam M|
| 1- 11 .36 .39 -.26 -.03 -.67 -.41 1.35 -.30 .7686 2 Anne F|
This displays a list of the local difficulty/ability estimates underlying the paired DPF analysis. These can be plotted directly from the Plots menu.
The DPF effects are shown ordered by CLASS within person (row of the data matrix).
TAP CLASS identifies the CLASS of items. KID is specified with ITEM=, e.g., the first CLASS is "1-"
OBSERVATIONS are what are seen in the data
COUNT is the number of observations of the classification used for DPF estimation, e.g., 11 "1-" items responses were made by person 1.
AVERAGE is the average observation on the classification, e.g., 0.18 is the average score class "1-' items by person 1.
COUNT * AVERAGE = total score of person on the item class.
BASELINE is the prediction without DPF
EXPECT is the expected value of the average observation when there is no DPF, e.g., 0.92 is the expected average for person 1 on item class "1-" without DPF.
MEASURE is the what the overall ABILITY measure would be without DPF, e.g., -2.94 is the overall person ability of person 1 as reported in Table 18.
DPF: Differential Person Functioning
DPF SCORE is the difference between the observed and the expected average observations, e.g., 0.92 - 0.89= -0.03
DPF MEASURE is the person ability for this item class, e.g., person 1 has a local ability of -3.52 for item CLASS "1-".
The average of DPF measures across CLASS for an item is not the BASELINE MEASURE because score-to-measure conversion is non-linear. ">" (maximum score), "<" (minimum score) indicate measures corresponding to extreme scores.
DPF SIZE is the difference between the DPF MEASURE for this class and the BASELINE measure ability, i.e., -3.93 - -4.40 = .48. Item 4 is .48 logits more difficult for class F than expected.
DPF S.E. is the approximate standard error of the difference, e.g., 0.89 logits
DPF t is an approximate Student's t-statistic test, estimated as DPF SIZE divided by the DPF S.E. with a little less than (COUNT-2) degrees of freedom.
Prob. is the probability of the t-value. This is approximate because of dependencies between the statistics underlying the computation.
Help for Winsteps Rasch Measurement Software: www.winsteps.com. Author: John Michael Linacre
|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|
|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: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr.||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|
|Sept. 4 - Oct. 16, 2015, Fri.-Fri.||On-line workshop: Rasch Applications, Part 1: How to Construct a Rasch Scale (W. Fisher), www.statistics.com|
|Sept. 9-11, 2015, Wed.-Fri.||In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric|
|Sept. 14-16, 2015, Mon.-Wed.||IACAT Conference: International Association of Computerized Adaptive Testing, Cambridge, UK, iacat.org|
|Sept. 14-16, 2015, Mon.-Wed.||In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric|
|Sept. 17-18, 2015, Thur.-Fri.||In-person workshop: Advanced Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric|
|Sept. 30 - Oct. 2, 2015, Wed.-Fri.||In-person workshop: IRT and Rasch analyses using R and Concerto (C. Gibbons), Cambridge, UK, www.psychometrics.cam.ac.uk|
|Oct. 16 - Nov. 13, 2015, Fri.-Fri.||On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com|
|Oct. 23 - Nov. 20, 2015, Fri.-Fri.||On-line workshop: Rasch Applications, Part 2: Clinical Assessment, Survey Research, and Educational Measurement (W. Fisher), www.statistics.com|
|Nov. 13, 2015, Fri.||In-person workshop: Rasch Models in Business Administration, in Homage to Professor Pedro Álvarez-Martínez, Tenerife, Canary Islands, www.institutos.ull.es|
|Dec. 2-4, 2015, Wed.-Fri.||In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric|
|March 18, 2016, Fri.||UK Rasch User Group Meeting, Durham, UK, www.rasch.org.uk|
|March 23-24, 2016, Wed.-Thur.||In-person workshop: Introduction to Rasch using Winsteps (W.Boone), Cincinnati OH, raschmeasurementanalysis.com|
|April 8-12, 2016, Fri.-Tues.||AERA Annual Meeting, Washington DC, www.aera.net|
|Aug. 12 - Sept. 9, 2016, Fri.-Fri.||On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com|
|The HTML to add "Coming Rasch-related Events" to your webpage is:|