## What’s a Z-Score and Why Use it in Usability Testing?

###### By Jeff Sauro . September 17, 2004 . Tags: Statistics

The Power of Z A common statistical way of standardizing data on one scale so a comparison can take place is using a z-score. The z-score is like a common yard stick for all types of data. Each z-score corresponds to a point in a normal distribution and as such is sometimes called a normal deviate since a z-score will describe how much a point