More isn’t always better. When it comes to UX testing, 5 is the golden number of testers to aim for according to Invision, a popular UX testing and prototyping tool and the Nielsen Norman Group, a consultant in the UX field.
As you increase the number of people involved, the less information you will gather per person. The first response you get will be 100% unique data. Any following responses will become less and less useful as your pool of knowledge grows.
Needing to find only five people to complete UX testing is much easier than finding and organizing a large group. It also becomes more economical if you are purchasing testers through a service like usertesting.com or offering reimbursement.
Having a UX testing group of only 5 should allow you to spend more time with each of them. Ask follow-up questions about their responses and get to understand their motivations and logic behind their behaviors. How do the users feel after interacting with the application? If they feel frustrated or lost, it doesn’t matter that they were able to log in and make a list of favorites. You never know what you might learn!
Most importantly, remember your goal when doing UX testing. Don’t get caught up in having x number of testers or marking items off a list. If you are testing a very intricate piece of functionality, you may need more than 5 testers. However, if you can’t easily reach a conclusion with your testing, it may be time to evaluate your plan and scale back to a feature set where using only 5 testers doesn’t seem so obscure.