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Meaningful Language Test Scores: Research to enhance score interpretation
Edited by Spiros Papageorgiou and Venessa F. Manna
[Innovations in Language Learning and Assessment 1] 2023
► pp. 14–34

Chapter 2
Considerations in developing vertical scales for language tests

| Educational Testing Service
| Educational Testing Service

This chapter provides a framework for building vertical scales, for language assessments in general and for the TOEFL® Family of Assessments in particular. Topics covered include aspects of vertical scale design (growth definitions, vertical articulation, data collection), statistical methods for vertical linking, and evaluation and maintenance of the resulting vertical scale. Also discussed are challenges associated with vertical scaling, as noted in the research literature, in general and as pertains to language proficiency assessments.

Article outline
  • Introduction
  • Vertical scale design
    • Growth definitions
    • Vertical articulation
    • Data collection design
  • Statistical methods for vertical linking
    • Hieronymus scaling
    • Thurstone scaling
    • IRT scaling
    • IRT scaling Decision 1: Choice of model
    • IRT scaling Decision 2: Separate vs concurrent calibration
    • IRT scaling Decision 3: Scores
  • Evaluation of a vertical scale
  • Maintenance of the vertical scale
  • Challenges with vertical scaling
  • Conclusion
  • References
Published online: 29 June 2023
DOI logo
https://doi.org/10.1075/illa.1.02mon
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