YES, yes and yes – of course: Usability testing is a method in user research. You are evaluating a system or product you design by observing people who think aloud while they use that system/product and solve pre-defined tasks and so help us to spot problems with the system or product.
Recruiting the right participants is a critical, very important and often neglected task when planning usability tests. In best case scenarios, your test participants should also slightly differ within a specified user group. This doesn’t necessarily mean that this has to be totally expensive and is not feasible for smaller companies or organizations.
If you’re going to run usability tests with people who don’t represent your actual users, the problem is, that you might not see incidents or problems that your actual users will have – because of the differences between who you run your test with and the people who will actually be using your system: Think only of expertise – are your actual users technically more sophisticated or do they tend to be relatively new and inexperienced with technology? Or think of cultural backgrounds. All those criteria (plus of course more) will have influence on how people will use the system you’re designing.
Or as userfocus says: „Screen for behaviours, not demographics“
Of course you CAN test with people who doesn’t fit in your criteria and who aren’t representative for the usage of the system you want to test – but then you have to be absolutely aware of that fact, and write it in your report – plus: think about the fact that your findings might or might not apply to the actual people/population who will use your system. You might spot problems or discover ways of thinking and cognitive schemas and mental models that don’t match your actual users.
Even if recruiting the right people may sometimes be a challenging task, it’s absolutely worth the effort, because it gives you a lot more information about how well your system is going to be designed for people who will be actually using it.
Image source: https://flic.kr/p/QHpkCL