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Comparison of Answer Copying Indices with Real Data
Author(s) -
Wollack James A.
Publication year - 2003
Publication title -
journal of educational measurement
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.917
H-Index - 47
eISSN - 1745-3984
pISSN - 0022-0655
DOI - 10.1111/j.1745-3984.2003.tb01104.x
Subject(s) - copying , scrutiny , statistics , type i and type ii errors , index (typography) , power index , test (biology) , power (physics) , statistical power , sample size determination , sample (material) , mathematics , computer science , law , political science , paleontology , physics , chemistry , mathematical economics , chromatography , quantum mechanics , world wide web , biology
This study investigated the Type I error rate and power of four copying indices, K‐index (Holland, 1996), Scrutiny! (Assessment Systems Corporation, 1993), g 2 (Frary, Tideman, & Watts, 1977), and ω (Wollack, 1997) using real test data from 20,000 examinees over a 2‐year period. The data were divided into three different test lengths (20, 40, and 80 items) and nine different sample sizes (ranging from 50 to 20,000). Four different amounts of answer copying were simulated (10%, 20%, 30%, and 40% of the items) within each condition. The ω index demonstrated the best Type I error control and power in all conditions and at all α levels. Scrutiny! and the K‐index were uniformly conservative, and both had poor power to detect true copiers at the small α levels typically used in answer copying detection, whereas g 2 was generally too liberal, particularly at small α levels. Some comments on the proper uses of copying indices are provided.