An indicator of the relative standing of a score within a normal distribution of scores, defined by its mean and standard deviation. By transforming raw scores to standard scores, the user can interpret intervals between any two score points in relation to a reference population. Z scores are a commonly used standard score transformation, providing a normal distribution with a mean of zero and a standard deviation of one.
Patricia Wheeler, Geneva D. Haertel, and Michael Scriven. (1992). Teacher Evaluation Glossary, Kalamazoo, MI: The Evaluation Center, Western Michigan University.