When setting up your usability test, you can define your users' demographic profile (country, language, gender, age, computer literacy), but you can also set screener questions to filter further and have the right users take your test.
You can have as many screener questions as you want. Keep in mind though, that if you set too strict criteria, there may not be enough testers to take your test.
Setting up a screener question is easy. You just enter a question to be asked to the users before taking the test, and you set the possible answers that they have to select from. If they choose an option that you have set as "ACCEPT", they are allowed to take the test. If they choose an option that you have set as "REJECT", they get rejected.
Since users will want to take tests, they may be tempted to guess the accepting options, so you have to setup your questions in a way that will not convey the accepting options.
Also, you should always add an "OTHER" option in the possible answers, because most probably there will be situations that are not covered by the options that you have set. This "OTHER" option should reject users.
If you need help or you are unsure about your screener questions, feel free to contact us.