September 24, 2014
Percentile rank, standard deviations, norm referenced? What does all this testing jargon mean?
Testing provides a way to gain a snapshot picture of your child’s ability to perform in certain subject or achievement areas. Measuring your child’s progress throughout the school year, from year to year, or over the course of a few years can enable evaluators to see if the student is making progress and to determine if intervention strategies are effective.
Types of Tests
To better understand some of the testing jargon, we can first identify the different types of tests.
- A standardized test is a test that is administered and scored in a consistent or “standard,” manner. There are two types of standardized test score interpretations: a norm-referenced score or a criterion-referenced score. Standardized test scores measure academic performance, not potential. In other words, they may tell you what your child knows today, but they say nothing about what he or she can learn tomorrow.
- Norm-referenced scores compare test-takers to a sample of peers. Norm-referenced tests determine a student’s placement on a normal distribution curve. This may include an Intelligence Quotient (I.Q.) test or a state achievement test. Standardized tests may better be known by their acronyms. Some common test results that you may see referenced in your child’s IEP are the Wechsler Individual Achievement Test 2nd (WIAT-II), and the Wechsler Intelligence Scale for Children (WISC V).
- Criterion-referenced tests are written with specific predetermined criteria in mind. Criterion-referenced scores compare test-takers’ answers to a formal definition of content, regardless of the scores of other students. This type of test may include academic tests such as spelling, math or reading comprehension tests.
Understanding Test Scores
Interpreting test scores can be confusing because different ways of measuring information can provide different perceptions of results.
- In order to determine how your child scored in comparison to others, a percentile rank is often used. A percentile rank is a score that tells the percent of students in a group with a lower score on the test than your child. This score shows your child’s rank in that group. Percentile ranks range from 1 to 99.
- 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 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.
- Test results for norm-referenced tests are usually reflected on a bell curve. In order to determine how well your child is doing compared to other students their age, read across the curve from left to right. The curve is broken down into sections. Each section represents the portion, or percentage, of scores that would fall at that point on the curve. The first, or smallest, section only represents a few scores (.13 % of the scores). The largest portion of the scores is in the two sections nearest the center where 68.26% of the scores would fall (or 34.13% for each of the two sections). The percentages add up to 100%, with 50% falling on each side of the curve. The left of the curve represents scores that fall below the average and the right side represents scores that fall above the average.
- A Grade Equivalent (GE) is a score that describes your child’s achievement on a grade level scale. The GE is a decimal number that describes academic performance in terms of grade level and month. For example, if your child (a sixth-grade student) receives a GE of 8.1 on the sixth grade vocabulary test, this means your child scored as well as an eighth grade student in the first month of the school year if given the same sixth grade vocabulary test. Similarly Age Equivalent test scores are scores that indicate the typical age of students (in years and months) who obtain a given score.
Parents are often overwhelmed by the test reports they receive from school personnel. In order to help establish true meaningful participation between parents and child study teams, it is essential that schools communicate information about student progress clearly, respectfully, and accurately. Information should be explained in language that parents can understand. Scores that are appropriate for the test should be discussed as well the child’s ranking comparatively. Alternately, instead of relying entirely on tests and scores, there are other types of information that can describe student performance. Direct observations and measurement of a child’s behavior, parental input, daily work samples, etc., in conjunction with test scores can all be used to measure progress.