Unlike intelligence test which are designed to measure ability or potential, achievement tests are designed to show what content knowledge a student has or has not mastered. Achievement test questions address content areas that include math, reading, social studies and science. Some tests may further divide these areas into sub-areas like math computation or language mechanics. Mastery, indicated by correct answers, requires both factual knowledge and the ability to apply knowledge to solve problems.
Norm-referenced tests compare a child’s performance against the performance of a large group of students of similar age and background called the norm group. Norm-referenced test yield scores that are expressed as a percentile rank, on a scale from 1 to 99. The average level of performance achieved by the norm group is set at the 50th percentile. Raw scores—the actual number of right and wrong answers—are adjusted mathematically to yield percentile scores which should not be confused with the similar-sounding term percentage, discussed later.
What do you do with your child’s scores from a standardized achievement test? Reporting scores to parents is often the weakest link in the chain of educational testing. Scores may be described using a variety of specialized terms that can be difficult to understand or, worse, misinterpreted. One of the most misunderstood concepts is the grade equivalent score.
Especially when your child is gifted, you may see test results that say your fifth grader is “reading at the ninth-grade level.” What does this phrase mean? The most common response is that your students reads as well as the average high school freshman.
This interpretation is incorrect. Remember, the test was made up of reading matter appropriate for fifth graders. There was no ninth-grade reading material on the test, so the test cannot determine whether a child can read ninth grade material. But the fifth-grade material can be read by a ninth grader, who will read more quickly and with greater understanding than the average fifth grader. So the correct conclusion is that your fifth grader reads fifth-grade material as well as the average ninth grader.
Another source of confusion is the distinction between percentage and percentile. A percentage score represents the number of correct answer, times 100, divided by the total number of test questions. If 40 of 50 questions are correct, then the student got 80 percent correct.
By contrast, a percentile score tells how your child compares to the children in the norm group, regardless of how many questions were actually answered correctly. The same 80 percent (40 or 50 correct) can lead to different percentile scores, depending on the performance of the norm group. If half of the students in the norm group got 40 or fewer questions correct, this score would be expressed as the 50th percentile. But if 90 percent of the norm group got 40 or fewer answers ,the same score would be expressed as the 90th percentile. The highest possible percentile is 99th, indicating that all 99 other raw scores of the 100 would be equal or lower.
Achievements test results may seem arcane at first glance, but properly understood, they provide important information about your child’s abilities. Tests can show how much of a curricular area your child has mastered, and results may point to areas of strength and those in need of attention. The more you learn, the easier it will be to make informed decisions about your child’s education future.
Michael S. Matthews, Ph.D.
(reprinted from Duke University Talent Identification Program)