How do usability specialists categorize usability problems?

In this paper for my Usability Testing and Assessment class, I looked at the various methods that usability expert categorize varying usability problems when performing a usability evaluation. Different methods exist usually revolving around the use of severity scales, of which there are many different kinds. However, in practice it seems a more simplified approach is most common. As a result of researching this paper and performing and moderating multiple usability tests, I am now able pick out what is most important and communicate those issues effectively.

Click here to download this paper.