Zscore minimum for reported bias terms (bias size/t-statistic value) = 0, 0

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Bias analysis calculates a bias measure, reported in Table 13 and Table 14, based on the data for which the elements include one from each of the facets specified. Most bias measures are small in logit size and statistically insignificant. This specification is a selection filter for which terms to report. The first control parameter places a lower limit on the absolute logit (in logits or user-units if user-scaled) of the bias measures to report. Thus, to report only bias measures that are outside of or equal to ±1 logit,

Zscore = 1 ; 1 logit

 

The second control parameter places a lower limit on the absolute value of the bias t-statistics to report. The t-statistic is obtained by dividing the bias measure by its standard error. With more than 30 observations, a t-statistic is approximately normally distributed, i.e., a z-statistic. To report only bias measures which have t-statistic outside of or equal to ±2:

Zscore = , 2 ; Leading comma, then 2 t-statistic units for bias control

 

To report bias measures which are either large in logits or significant statistically or both, specify both control parameters:

Zscore = 1,2 ; 1 logit or 2 t-statistic units

 

To report all bias measures:

Zscore= 0,0 ; include everything

 

Historical note: Facets used to assume that bias terms have approximately infinite degrees of freedom. Consequently they were reported as t-statistics with infinite degrees of freedom. These have the form of a unit-normal distribution, which is the same distribution as z-scores. Facets now reports bias significance using t-statistics with more exact finite degrees of freedom.

For reporting purposes, the absolute value of the t-statistic is compared with the specified second value in Zscore = bias-size, t-statistic value.


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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 2nd. Ed., Bond & Fox (Winsteps) 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 (Facets) Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr. (Facets)
Statistical Analyses for Language Testers, Rita Green (Winsteps, Facets) Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement
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Coming Rasch-related Events
June 19-21, 2013, Wed.-Fri. SIS 2013 Conference on Advances in Latent Variables: Methods, Models and Applications, Brescia, Italy, meetings.sis-statistica.org/index.php/sis2013/ALV
July 1 - Nov. 30, 2013, Mon.-Sun. Online Course: Introduction to Rasch Measurement Theory (D. Andrich, RUMM), www.education.uwa.edu.au/ppl/courses
July 5 - Aug. 2, 2013, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps), www.statistics.com
July 15, 2013, Monday Application deadline: UIC Educational Research Methodology online graduate certificate program, www.go.uic.edu/OnlineMESA
July 22, 2013, Monday Submission deadline: 2014 AERA Annual Meeting, Philadelphia PA, www.aera.net
Aug.1-5, 2013, Thur.-Mon. TERA-PROMS Annual Meeting, Kaohsiung, Taiwan, tera.education.nsysu.edu.tw
Aug. 9 - Sept. 6, 2013, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com
Aug. 22, 2013, Thursday. Symposium in honor of Svend Kreiner, Copenhagen, Denmark, biostat.ku.dk/kreinersymposium
Sept. 4-6, 2013, Wed.-Fri. IMEKO TC1-TC7-TC13 Symposium: Measurement Across Physical and Behavioural Sciences, Genoa, Italy, www.imeko-genoa-2013.it
Sept. 13 - Oct. 11, 2013, Fri.-Fri. On-line workshop: Rasch Applications in Clinical Assessment, Survey Research, and Educational Measurement (W.P. Fisher), www.statistics.com
Sept. 18-20, 2013, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 23-25, 2013, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 26-27, 2013, Thurs.-Fri. In-person workshop: Advanced Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Oct. 18 - Nov. 15, 2013, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
Oct. 20 - Oct. 25, 2013, Sun.-Fri. International Association for Educational Assessment (IAEA) 39th Annual Conference, Tel Aviv, Israel, www.iaea-2013.com
Dec. 11-13, 2013, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
March 12-14, 2014, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
April 3-7, 2014, Thurs.-Mon. AERA Annual Meeting, Philadelphia PA, www.aera.net
May 14-16, 2014, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
May 19-21, 2013, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
July 4 - Aug. 1, 2014, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps), www.statistics.com
Aug. 8 - Sept. 5, 2014, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com
Sept. 10-12, 2014, Wed.-Fri. In-person workshop: Introductory Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 12 - Oct. 10, 2014, Fri.-Fri. On-line workshop: Rasch Applications in Clinical Assessment, Survey Research, and Educational Measurement (W.P. Fisher), www.statistics.com
Sept. 15-17, 2014, Mon.-Wed. In-person workshop: Intermediate Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
Sept. 18-19, 2014, Thurs.-Fri. In-person workshop: Advanced Rasch (A. Tennant, RUMM), Leeds, UK, www.leeds.ac.uk/medicine/rehabmed/psychometric
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