For most tests on our self-service SaaS platform, 60-90% of total testers will complete your test - depending on incentives, complexity, overall enjoyment of the product, and other factors (such as weekends and holidays).
Our system onboards the number of testers you select when you build your test if we are able to find that amount in our audience, so you should expect to have a smaller percentage actually complete your test. If you are looking for an exact target, you should consider onboarding a few extra people, but also be comfortable with incentives being higher if a large percentage complete your test.
The main scenario where you would receive less testers than requested is if your targeting criteria (age, location, income, etc) or screening survey is too strict and limits how many testers are invited or accepted. Other scenarios include:
Complex test instructions or confusion from testers
Difficulty accessing your product or bugs that prevent testers from participating
Please note for bug tests: Testers who submit bugs but don't complete all tasks may still count in your tester total due to their time and commitment to try to participate and discovering bugs, even if those bugs prevented them from participating in all tasks.