What about abnormal or deviant scores?
Scores can be compared to identify those at the extremes or tails of a distribution.

Let's go back to the Physics test.
You are the Physics professor and the chair of the department wants to know what scores on your test cut off the top 5% of the students and the lowest 5%. The former get an award and the latter get a scolding!

Here's the answer:
I looked up the Z-Score that cuts off 5% in the tails. The score is 1.64 as you can see in most Z tables. Thus, on my Z-Score ruler, the test scores would have to be plus or minus 1.64 Z units from the mean. One Z unit (our inch, so to speak) equals 10 points. So I get the picture below and my two cut-offs of 33.6 (low) and 66.4 (high).