Measuring Up: What Educational Testing Really Tells Us

by Daniel Koretz

Clearly, the more reading and writing a math test requires, the more likely it is that the scores of dyslexic students will be adversely affected by their disabilities. But is this adverse effect a bias that should be offset by accommodations, or is it in fact a realistic indicator of lower proficiency? The answer, the NRC panel explained, is that it depends on the specific inference you base on the scores—that is, it depends on what you mean by “proficiency in mathematics.” On the one hand, if you were using scores to estimate skills such as computational facility, the performance of dyslexic students on math tests that require substantial reading clearly would be biased downward, because their difficulties in reading would make it hard for them to demonstrate their computational skills. On the other hand, if you were using scores to estimate how well students can apply such skills to real-world problems of the sort they may encounter later, including mathematics problems embedded in text, the scores would be less biased.