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Introduction to Many-Facet Rasch Measurement

Analyzing and Evaluating Rater-Mediated Assessments. 2nd Revised and Updated Edition


Thomas Eckes

Since the early days of performance assessment, human ratings have been subject to various forms of error and bias. Expert raters often come up with different ratings for the very same performance and it seems that assessment outcomes largely depend upon which raters happen to assign the rating. This book provides an introduction to many-facet Rasch measurement (MFRM), a psychometric approach that establishes a coherent framework for drawing reliable, valid, and fair inferences from rater-mediated assessments, thus answering the problem of fallible human ratings. Revised and updated throughout, the Second Edition includes a stronger focus on the Facets computer program, emphasizing the pivotal role that MFRM plays for validating the interpretations and uses of assessment outcomes.
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1. Introduction


1.  Introduction

This chapter introduces the basic idea of many-facet Rasch measurement. Three examples of assessment procedures taken from the field of language testing illustrate the broader context of its application. In the first example, examinees respond to items of a reading comprehension test. The second example refers to a writing performance assessment, where raters evaluate the quality of essays. In the third example, raters evaluate the performance of examinees on a speaking assessment involving live interviewers. Having discussed key concepts such as facets and rater-mediated assessment, the general steps involved in adopting a many-facet Rasch measurement approach are pointed out. The chapter concludes with an outline of the book’s purpose and a brief overview of the chapters to come.

1.1    Facets of measurement

The field of language testing and assessment traditionally draws on a large and diverse set of procedures that aim at measuring a person’s language ability or some aspect of that ability (e.g., Alderson & Banerjee, 2001, 2002; Bachman & Palmer, 1996; Spolsky, 1995). For example, in a reading comprehension test examinees may be asked to read a short text and respond to a number of questions or items that relate to the text by selecting the correct answer from several options given. Examinee responses to items may be scored either correct or incorrect according to a well-defined key. Assuming that the test measures what it is intended to measure, that is, when the number-correct score can be interpreted in terms...

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