It wasn’t too long ago that when we needed to stock our pantries or fridges, we’d head out to a grocery store and select our items. Nowadays, more people are shopping online, skipping the grocery store altogether. This is but one example of how most of what we consume nowadays is done online. The past few years of living under Covid-19 conditions has only accelerated the online phenomenon.
Any retailer with an online presence knows how important UX design is to the bottom line. A poorly designed webpage will frustrate users, likely sending them to seek out easier-to-use alternatives. Given the ubiquity of online sales, we are seeing a steep increase in companies conducting usability tests. Usability tests are great at uncovering problems with the design; discovering opportunities to improve the design, and, learning about user behavior and preference when interacting with the design.
There are similarities for market researchers when designing a usability study and focus groups, both require recruiting participants who have some familiarity of the topic or design being tested, and both require skilled moderators who can home in on problem areas. As with any qualitative or quantitative study, you need to know how many people to recruit to participate. We’ve written about the ideal number of participants to recruit for focus groups, but what about usability studies?
Before you read any further, let us first reiterate that as with any qualitative study, there is no ‘one size fits all’ number. Each usability study is unique and there is still considerable debate in the industry about ‘the right number of participants’, if it even exists at all. Rather than leave you to de-code what the ideal number is, we’ll break it down for you.
What’s the probable impact of the usability test?
Not all usability studies are high stakes, but how do you know? If you’re testing a core feature that would impact a lot of users, then you can safely assume a higher impact. If you’re doing a more granular study that looks at what order to list your tabs, or where to place a button, then you can consider your study as having a lower impact. Once you determine if you’re usability study is high or low impact then the following will help with knowing how many people to recruit for your study.
High impact study=more participants
Low impact study=fewer participants
How many rounds of testing will you conduct?
Obviously, your budget will determine how many rounds you can afford, but with most qualitative studies, you’ll want more than one round. As with focus groups or other qualitative methodologies, the moderator will get a baseline of responses or reactions in the first round, and can then build upon that in subsequent rounds. Taking an iterative approach to qualitative studies allows you to discover additional insights. Using an iterative approach to usability testing, you can first start with a smaller group of candidates and then conduct additional rounds until statistical significance is reached.
More usability rounds=fewer participants
Fewer usability rounds=more participants
At what stage in the product development cycle are you?
If you’re early in the development cycle, the likelier you’ll uncover big errors in your design. Typically, such errors are found quickly, so you can recruit fewer participants for early-stage development. As you build out your product and are in later-design phases, you’ll want to budget for more participants or more rounds, as the errors or roadblocks will be less obvious and egregious, but no less important to know about.
Early-stage product development=fewer participants
Later-stage product development=more participants
But what’s the number?!
Fewer and more participants is not definitive, so what’s the ideal number that you should have fewer or more than? At the risk of sounding wishy-washy, there is no perfect number, but you’d be safe to go with five. If you use 5 as the average usability study size, then you can go higher or lower when thinking about where you’re at in your usability testing: high or low impact, number of rounds of testing, and product development stage.
When it comes to recruiting, our teams of recruiters are here to help. We have years of experience matching the best participants with all types of studies. From usability testing, to consumer research studies, to medical and healthcare studies, our specialty is finding ideal participants for your study.