In an increasingly data-driven world, it is more important than ever for students as well as professionals to better understand basic statistical concepts. 100 Questions (and Answers) About Statistics addresses the essential questions that students ask about statistics in a concise and accessible way. It is perfect for instructors, students, and practitioners as a supplement to more comprehensive materials, or as a desk reference with quick answers to the most frequently asked questions.

# What Is a z Score, and How Is It Computed?

### What Is a z Score, and How Is It Computed?

There are so many different studies that if we want to compare performances on a certain variable from different distributions, we need a metric with some common basis. Standard scores allow us to do just that. These scores are comparable to one another because they all are expressed in units of standard deviations.

In the social and behavioral sciences, as in other fields, the most frequently used standard score is the z score. The z score is called a variety of other names, such as z value, normal score, and standardized variable. And there are other types of standard scores, such as T scores.

Here is the formula for computing a standard score:

$z=\frac{X-\overline{X}}{s},$

where

• z is the z ...
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