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What are the limitations of stanine scores?
• They should not be used in computing group statistics or in determining gains.
• They give only very general indications of a student's relative standing in a
particular content area.
Grade equivalent scores
Grade equivalent scores use a scale based on grade levels and months to estimate how well students perform. These scores reflect the median score of students across several grade levels during the month the test was normed. For instance, the median test score for first graders in the seventh month of the school year (April) would convert to a score of 1.7, for second graders the score would be 2.7, for third graders the score would be 3.7, and so forth.
Grade equivalent scores are often misunderstood. For example, if a fourth grader received a grade equivalent score of 7.0 on a fourth grade reading achievement test, some people may assume that the fourth grader has mastered seventh grade material. However, the score actually means that the fourth grader reads fourth grade material as well as the typical beginning seventh grader (in September) would read the same fourth grade material.
As with percentile scores, you should use grade equivalent scores only to describe a student's standing in relation to the norming group at the time of testing. You should not average grade equivalent scores to describe groups, and you should not subtract them to compute gains.
As with differences in percentile scores, differences in grade equivalent scores do not mean the same thing across the entire scale.
How are grade equivalent scores distributed?
Figure 5 shows an example of how grade equivalent scores are distributed when raw scores are distributed normally. The y axis shows the proportion of students and the x axis shows the grade equivalents. Vertical lines have been drawn to indicate each standard deviation unit.
Note that this is just an example, because grade equivalent scores are not defined by the model but rather by the actual performance on the test by students in higher and lower grade levels.
Notice that relatively few correct responses translate to large differences in grade equivalent scores for students who achieve very high and very low scores. Because of this, grade equivalent scores do not estimate group ability well and you should not use them to evaluate gains over time.
Rudner, L. and W. Schafer (2002) What Teachers Need to Know About Assessment. Washington, DC: National Education Association.
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