Understanding Test Scores - TeachersAndFamilies

Understanding
Test Scores

A primer for parents...


Introduction

Norm-Referenced Tests

Norm-referenced tests compare an individual child's performance to that of his or her classmates or some other, larger group. Such a test will tell you how your child compares to similar children on a given set of skills and knowledge, but it does not provide information about what the child does and does not know. Scores on norm-referenced tests indicate the student's ranking relative to that group. Typical scores used with norm-referenced tests include:

Percentiles. Percentiles are probably the most commonly used test score in education. A percentile is a score that indicates the rank of the student compared to others (same age or same grade), using a hypothetical group of 100 students. A percentile of 25, for example, indicates that thestudent's test performance equals or exceeds 25 out of 100 students on the same measure; a percentile of 87 indicates that the student equals or surpasses 87 out of 100 (or 87% of) students. Note that this is not the same as a "percent"-a percentile of 87 does not mean that the student answered 87% of the questions correctly! Percentiles are derived from raw scores using the norms obtained from testing a large population when the test was first developed.

Stanines. Stanines are essentially groups of percentile ranks, with the entire group of scores divided into 9 parts, with the largest number of individuals falling in the middle stanines (3-7), and fewer students falling at the extremes. Few tests in common usage today use stanines, although these scores can be useful in understanding the relative range of a student's performance.

Standard scores. A standard score is also derived from raw scores using the norming information gathered when the test was developed. Instead of reflecting a student's rank compared to others, standard scores indicate how far above or below the average (the "mean") an individual score falls, using a common scale, such as one with an "average" of 100. Standard scores also take "variance" into account, or the degree to which scores typically will deviate from the average score. Standard scores can be used to compare individuals from different grades or age groups because all scores are converted to the same numerical scale. Most intelligence tests and many achievement tests use some type of standard scores. For example, a standard score of 110 on a test with a mean of 100 indicates above average performance compared to the population of students for whom the test was developed and normed.

Age/Grade Equivalent scores. Some tests provide age or grade equivalent scores. Such scores indicate that the student has attained the same score (not skills) as an average student of that age or grade. For example, if Sally obtains a grade-equivalent score of 3.6 on a reading comprehension test, this means that she obtained the same score as the typical student in the sixth month of third grade. Sally may or may not have acquired the same skills as the typical third grader. Age/grade scores seem to be easy to understand but are often misunderstood, and many educators discourage their use.

Standard scores, percentile ranks, and stanines can be compared using the "normal" or bell-shaped curve. Most tests used in education are developed in order to yield a standard curve of scores, where the majority of all students would fall within a small range (or one "standard deviation") of the mean or average score, and where 50% of all students would fall above and 50% would fall below the average score. Some tests, however, do not have such "normal" distributions of scores, and these different types of scores may not be comparable.

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Adapted from "Understanding Test Scores: A Handout for Parents" by Andrea Canter,
in Helping Children at Home and School: Handouts from Your School Psychologist
(National Association of School Psychologists, 1998).
Copyright © 2002 by The Source for Learning, Inc. • All rights reserved.
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