Lynch School of Education

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TITLE:
Summarizing Change in Test Scores: Shortcomings of Three Common Methods. ERIC Digest.

DOCUMENT TYPE: Report

Link to Document: Summarizing Change in Test Scores: Shortcomings of Three Common Methods. ERIC Digest.

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ABSTRACT:
This Digest introduces the advantages and disadvantages of three commonly used methods of reporting test score changes: (1) change in percentile rank; (2) scale or raw score change; and (3) percent change. The change in percentile rank method focuses on the increase or decrease of the mean percentile ranking for a group of students. This method has two main problems. The first is that calculating the mean percentile rank based on an individual's percentile ranks can provide an inaccurate estimate of a group's mean performance. The second is that, because of unequal intervals separating percentile ranks, changes in percentile ranks represent different amounts of growth at each point on the scale. A second method is scale or raw score change. The main drawback to this methods is that when raw scores are used to determine change, it is difficult to compare change across tests with different score ranges. A third approach, that of reporting percent change, causes further distortion. resulting in a statistic that is difficult to interpret and misleading. All of these methods should be avoided when summarizing change in test scores. A separate Digest suggests better ways to summarize changes. (SLD)