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Impossible Scores Resulting in Zero Frequencies in the Anchor Test: Impact on Smoothing and Equating

Author(s):
Puhan, Gautam; von Davier, Alina A.; Gupta, Shaloo
Publication Year:
2008
Report Number:
RR-08-10
Source:
ETS Research Report
Document Type:
Report
Page Count:
26
Subject/Key Words:
Test Equating, Loglinear Smoothing, Scaled Scores, Anchor Test Study

Abstract

Equating under the external anchor design is frequently conducted using scaled scores on the anchor test. However, scaled scores often lead to the unique problem of creating zero frequencies in the score distribution because there may not always be a one-to-one correspondence between raw and scaled scores. For example, raw scores of 17 and 18 may correspond to scaled scores of 150 and 153, thereby creating zero frequencies for scaled scores of 151 and 152.

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