Gain_Scores

Gain_Scores - Applied Psychological Measurement...

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http://apm.sagepub.com Applied Psychological Measurement DOI: 10.1177/014662169602000106 1996; 20; 59 Applied Psychological Measurement Richard H. Williams and Donald W. Zimmerman Are Simple Gain Scores Obsolete? http://apm.sagepub.com/cgi/content/abstract/20/1/59 The online version of this article can be found at: Published by: http://www.sagepublications.com can be found at: Applied Psychological Measurement Additional services and information for http://apm.sagepub.com/cgi/alerts Email Alerts: http://apm.sagepub.com/subscriptions Subscriptions: http://www.sagepub.com/journalsReprints.nav Reprints: http://www.sagepub.com/journalsPermissions.nav Permissions: http://apm.sagepub.com/cgi/content/refs/20/1/59 Citations at LOUISIANA STATE UNIV on July 7, 2009 http://apm.sagepub.com Downloaded from
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59 Are Simple Gain Scores Obsolete? Richard H. Williams, University of Miami Donald W. Zimmerman, Carleton University It is widely believed that measures of gain, growth, or change, expressed as simple differences between pretest and posttest scores, are inherently unreliable. It is also believed that gain scores lack predictive validity with respect to other criteria. However, these conclu- sions are based on misleading assumptions about the values of parameters in familiar equations in classical test theory. The present paper examines modified equa- tions for the validity and reliability of difference scores that describe applied testing situations more realisti- cally and reveal that simple gain scores can be more useful in research than commonly believed. Index terms: change scores, difference scores, gain scores, measurement of growth, reliability, test theory, validity. Over a quarter century ago, Cronbach & Furby (1970) and many other authors (e.g., Gulliksen, 1950; Lord & Novick, 1968) concluded that simple differences between pretest and posttest scores have ques- tionable value in behavioral and social science research. Yet this conclusion seems incompatible with the intuition of researchers in many disciplines who assume that measures of gains, changes, differences, growth, and the like are meaningful in experimentation, program evaluation, educational accountability studies, and the investigation of developmental growth and change. During the past two decades, many researchers using difference (or gain) scores have had difficulty justifying the use of such measures, even when they appear to yield interesting and reproducible findings. However, recent research on this topic has provided results favorable to simple gain scores (e.g., Collins Cliff, 1990; Llabre, Spitzer, Saab, Ironson, & Schneiderman, 1991; Rogosa & Willett, 1983; Willett, 1989; Williams, Zimmerman, Rich, & Steed, 1984a, 1984b; Wittman, 1988; Zimmerman & Williams, 1982a, 1982b). There is also a rather
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This note was uploaded on 11/23/2011 for the course PHYS 6198 taught by Professor Cohor during the Summer '10 term at LSU.

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Gain_Scores - Applied Psychological Measurement...

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