Constructing test items for standardized tests of achievement, ability, and aptitude is a task of enormous importance. The interpretability of a test's scores flows directly from the quality of its items and exercises. Concomitant with score interpretability is the notion that including only carefully crafted items on a test is the primary method by which the skilled test developer reduces unwanted error variance, or errors of measurement, and thereby increases a test score's reliability. The aim of this entire book is to increase the test constructor's awareness of this source of measurement error, and then to describe methods for identifying and minimizing it during item construction and later review.