Test Scores - What do they really mean???

Parents and teachers are often faced with reports or other forms of test results and often have trouble fully understanding what they mean. Whether it involves IQ scores, achievement scores, behavior ratings, etc., it is very important to understand what the scores mean. Here is a brief tutorial which may help to understand the most commonly used standardized test scores.

Standard Scores (frequently used for IQ)

Percentile Ranks

Scaled Scores


Grade Equivalents and Age Equivalents

Before you can begin to understand what a given test score may mean you must first understand the scale that is being used. For example, an IQ score of 115 is the same as a percentile rank of 84, a scaled score of 13, and a t-score of 60. So if you don't know the type of score or the scale used, it is meaningless. Regardless of the scale, it is usually most useful to interpret a student's test score by comparing it to whatever the 'average' score is on the scale which is being used. You may be surprised at how wide the 'average range' can be.....

IQ Scores or 'Standard Scores' are typically used for individual intelligence and achievement tests. The key factors to understand about these scores include:

  • A perfectly average score is 100

  • The average range is roughly from 90 to 110

  • The 'broad normal range' of test scores is 70 to 130

If a student scores in the 90 to above range there probably isn't much cause for concern. Scores in the 80s would indicate somewhat more significant concern with scores in the 70s suggesting considerable difficulty. Scores below 70 would be outside of the 'normal range' and indicate severe difficulty.

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Percentile Ranks are generally provided for all types of standardized tests and provide the most direct reference to how a student performed in comparison with the general population of students his or her age. In other words, if a student scores at the 60th percentile it simply means that his/her performance is estimated to be equal to or better than 60 percent of the general population. Here are the most important factors to understand about percentile ranks:

  • A perfectly average score is 50

  • The average range is roughly from 25 to 75

  • The 'broad normal range' of scores is 2 to 98

Percentile ranks are often difficult to understand because the scale is not uniform from one end to the other. The middle 'average' area is very broad whereas the 'ends' become very narrow. Scores at or above the 25th percentile are probably not of any significant concern. Scores between the 10th and 25th percentiles may be of moderate concern, and scores below the 10th percentile suggest relatively significant difficulty.

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Scaled Scores are sometimes used for subtests (e.g. the Wechsler Intelligence Scale for Children - WISC). The important factors to note about these scores include:

  • A perfectly average score is 10

  • The average range is roughly from 8 to 12

  • The 'broad normal range' of scores is 4 to 16

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T-Scores are typically used for behavior rating scales. The important factors to note about these scores include:

  • A perfectly average score is 50

  • The average range is roughly from 43 to 57

  • The 'broad normal range' of scores is 30 to 70

It should be noted that scores on behavior rating scales are typically interpreted in a manner which is exactly the opposite of other tests. In other words, for behavior ratings, low scores are considered 'good' whereas high scores would indicate areas of concern. In general, t-scores in the 60s suggest moderate or 'at-risk' concern while t-scores of 70 or above indicate severe or 'clinically significant' concern.

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Grade Equivalent and Age Equivalent scores are sometimes provided for individual and group achievement tests although they are no longer widely used because they tend to be extremely misleading. The important factors to note about these scores include:

  • A perfectly average score is that which falls exactly at the grade or age of the student being tested

  • The average range varies and is quite small (a few months) at early grades/ages and very broad (several years) at higher grades/ages

  • The 'broad normal range' of scores cannot be determined

Grade equivalent and age equivalent scores are sometimes requested by parents or teachers due to a desire to know if the student is 'working at grade level'. Although this may seem like a reasonable expectation, due to the broad distribution of skills at each grade/age level (especially for older students) it is 'normal' and even necessary (from a statistical point of reference) for a relatively large portion of students to perform both above and below grade level. In fact, by 7th or 8th grade, the 'average range' for grade equivalent scores extends from about 5th grade to 10th grade. This is not an indication of a failing educational system, but merely reflects the normal distribution of skills among the normal student population. Even if all students were to improve their skills by 100% the distribution of skills would remain the same resulting in the same number of students performing below grade level. Regardless of its intent, 'No Child Left Behind' will not change this. For these reasons it is highly recommended that you avoid any attempt to interpret grade or age equivalent scores!!

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