How do you interpret standard scores, percentiles, and z-scores?

• A. Percentiles show rank relative to peers.
• B. Standard scores are scaled with a mean and SD; percentiles show rank relative to peers; z-scores express distance from the mean in SD units.
• C. Z-scores express the sum of all test items.
• D. Standard scores are just raw numbers.

Answer: (B)

Interpreting these score types hinges on what each one communicates about a student’s position in a distribution. Standard scores are scaled scores with a fixed mean and standard deviation, which makes it possible to compare performance across different tests and interpret where a score sits relative to the average in SD units. Percentiles show rank relative to peers: they tell you the percentage of peers who scored at or below a given score, giving a sense of relative standing within the group. Z-scores express distance from the mean in standard deviation units, offering a precise measure of how far and in which direction a score lies from the center of the distribution.

Together, this combination lets you see not just where a student falls on a single scale, but how their performance compares across tests (standard scores), how they rank among peers (percentiles), and how far they are from the average in standard deviation terms (z-scores). The statements that z-scores sum items or that standard scores are just raw numbers don’t fit, since z-scores quantify deviation in SD units, and standard scores are scaled metrics with a defined mean and spread, not raw totals.