ERIC Number: EJ1135072
Record Type: Journal
Publication Date: 2017
Abstractor: As Provided
The Accuracy of Aggregate Student Growth Percentiles as Indicators of Educator Performance
Castellano, Katherine E.; McCaffrey, Daniel F.
Educational Measurement: Issues and Practice, v36 n1 p14-27 Spr 2017
Mean or median student growth percentiles (MGPs) are a popular measure of educator performance, but they lack rigorous evaluation. This study investigates the error in MGP due to test score measurement error (ME). Using analytic derivations, we find that errors in the commonly used MGP are correlated with average prior latent achievement: Teachers with low prior achieving students have MGPs that underestimate true teacher performance and vice versa for teachers with high achieving students. We evaluate alternative MGP estimators, showing that aggregates of SGP that correct for ME only contain errors independent of prior achievement. The alternatives are thus more fair because they are not biased by prior mean achievement and have smaller overall variance and larger marginal reliability than the Standard MGP approach. In addition, the mean estimators always outperform their median counterparts.
Descriptors: Teacher Evaluation, Teacher Effectiveness, Value Added Models, Achievement Gains, Error of Measurement, Alternative Assessment, Evaluation Methods, Evaluation Criteria, Prior Learning, Test Reliability, Test Validity, Test Bias, Low Achievement, High Achievement
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Publication Type: Journal Articles; Reports - Research
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