5) Who and when to test?

Test users

Reqruit test users that are as representative users as possible. In order to get statistical significant metrics, you need to test at least 20 users for each task.

Methods

You could use an online usability metrics system and recruit users on your website and make them complete tasks online.

It's more expensive to invite users to your test lab and make a regular usability test. However, this option gives you better validity as you have control over more things, like misunderstandings. It also gives you additonal qualitative data.

Testing interval

Test as often you feel its useful with new data. Before/after new design releases, competititors' new designs, new functionalities/user goals.

Introduction to usabilty metrics

1. What is usability?
2. Usability methods
3. Usability metrics
4. Usability goals
5. Who and when to test?