However, when several common conditions are met—when tests assess broad domains, are constructed of items that have a reasonable range of difficulty, and are scaled using most of the currently common methods—scale scores often show a roughly normal distribution, with many students clustered near the average and progressively fewer as one goes both lower and higher. Exceptions are not rare, however. If a test is easy for the students taking it, the distribution will not be normal—it will be asymmetrical, with a tail of low scores but many students piled up near the maximum score. A test that is
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