User interviews are a fantastic way to gain valuable insights and ideas from your users. But when it comes to actually conducting interviews, many researchers don’t know how many users to include in their sample. If you’ve been wondering “How many user interviews should you do to get the best results?” then you’ve come to the right place.
Knowing the number of user interview participants to interview helps you get the best insights and helps you save on expenditure and time. You don’t want to spend extra money on research that you don’t need. However, not getting enough research will leave you in a bit of a pickle.
That’s why we’re here to help you find the perfect amount of user interviews, as well as a handy tool that will make your UX research ten times easier!
How Many User Interviews (Participants) Should You Do For Your UX Research?
The recommended number of participants needed for an exploratory UX interview will depend on a variety of factors, including the scope and objectives of your research, the time and resources available, and the complexity of your target audience.
Generally speaking, you’ll want to conduct a minimum of 5-6 user interviews to identify and validate key user needs and design requirements. This allows you to gather a diverse range of perspectives and insights, and to identify common themes and patterns in user behavior and feedback.
The most obvious things to change will be the ones that crop up over and over again. If, however, your research is focused on a specific user group or a complex problem, you may find it helpful to conduct more interviews in order to gather sufficient data.
Ultimately, the number of user interviews you conduct should be based on your research goals and the specific needs of your project. Nobody can decide this for you.
A Mathematical Model
The two founders of the Nielsen Norman Group, Jakob Nielsen and Tom Landauer, created a mathematical model that suggested that interviewing five users helped identify about 85% of the issues in an interface.
They argued that the best investment would be to interview five users, find your 85% of the issues, fix them, and then interview five more users. They repeatedly stated that it wasn’t wise to try and find 100% of the UX issues in one round of interviews because it would waste too much time and money, not to mention more issues are bound to arise during the redesign phase.
So How Many UX Research Interviews Do You Need?
So, how many interviews are enough to conduct your research? That completely depends on your research goals and objectives. You should also ensure you have enough UX research interview questions that span the full scope of your design. If you don’t ask the right questions, you won’t get the right answers.
If you’re looking for user feedback on a new feature, you might only need 4-5 interviews. But if you’re trying to understand user behavior or uncover user needs, you may need a few rounds of five interviews.
On average, it’s ideal to have two rounds of five interviews, fixing the original issues before the second round occurs. This allows you to get a good mix of perspectives and opinions without spending too much time and money conducting interviews. Of course, there are always exceptions to this rule. For example, if you’re looking for super specific insights then you may need to adjust the number of participants accordingly.
How to Determine How Many Interviews to Conduct
The recommended number of participants needed for an exploratory UX interview varies depending on many factors. Here are some of them:
Your Goals and Objectives for the Research
Knowing what you want to achieve from the user interviews will help you understand how many user interviews you need. For example, if your objective is to get user feedback on a couple of features, a smaller number of user interviews can suffice. But if your objectives are more detailed, such as understanding user behavior or uncovering user needs, you might need more user interviews to get the insights you’re looking for.
Saturation (Seek Diminishing Returns)
It may be difficult to tell how many users you need for your interviews, but it is far easier to tell when you’re approaching saturation. By that, we mean having the majority of the answers you were looking for.
If you want to know how many interviews are enough, the truth is, you can uncover the vast majority of issues from just a few users. For this reason, instead of searching for a golden-but-rigid-number to interview, look for golden insights instead. You can reduce additional user interviews as you approach the results of the goal or objectives you set for your research project.
As a researcher, the number one goal is to get all the great ideas, behavioral patterns, stories, and experiences of your users based on your objectives. The number of participants you need to get those insights comes second. To make this work, you can start your interviews with open-ended questions that trigger them to go both broad and deep about their motivations, habits, and how they get things done using your service.
Seek diminishing returns when planning for users. How many users do you need to arrive at a comfortable point of not conducting any more interviews? At a certain point, you begin to gain less and less new information until you reach saturation. When your sessions start to feel repetitive, with no new opinions or information, it’s a sure-fire sign that it’s time to end your interview process and start fixing the highlighted issues.
Pro Tip: Record Your Interviews
With tl;dv, you can record your interview sessions for free. It doesn’t matter whether you use Zoom or Google Meet, you’ll be able to review your interviews after each one, and you can even tag your colleagues with timestamps at important parts to show what they need to fix. This is integrated directly with Slack and other work tools so they can literally click the timestamp and be redirected to the exact moment of the recording that’s relevant to them!
When you record your interviews with tl;dv, you also get a free transcript, allowing you to pluck quotes directly from the interview. There’s no better way to illustrate user feedback than in the user’s own voice! Instead of monotone, text-based bullet points, you can capture the real emotion associated with a user’s pain points. Our remote UX research tool offers all these amazing features and much, much more.
There is No Magic Number
As already stated, there is no magic number for the amount of user interviews you need to conduct. That’s not necessarily a bad thing though. Research and user interviews are highly subjective. You can never know how many users you need to gain your insights. It could be two, it could be forty-two.
Instead of focusing on a golden number, each UX researcher should focus on their product and its specific requirements; it’s within your own project that the number of participants you need lies.
There are several researchers that have suggested an ideal number for how many user interviews you should conduct. Here are some of them:
- The Nielsen Norman Group recommends that five test participants is enough per interview round.
- Mark Mason reviewed 560 qualitative research papers in 2010 and summarized that the number of participants should be between 1 and 95. Nice conclusion, Mark! Helps a bunch. The average from his research was 31, but it came with a large standard deviation (which you can determine using a standard deviation calculator). Mason’s work is largely unhelpful, and mostly based on the number of participants that other researchers ended up using, rather than whether those interviews were revealing new insights.
- In an ethnographic study, Greg Guest and Co arrived at the number of 12 interviews. Their research shows that 97% of issues are covered after 12 user interview participants, while 94% came from the first 6 of the participants. This study is similar to the findings of the NN Group, which suggest you run fixes after the first round of interviews, and then proceed with more.
The most important thing to note from this is that you will need as many user interviews as your objectives call for. Running them in stages, with fixes in between, seems like the most logical approach, as each stage will be more advanced with potentially new issues arising as you go on.
What Topic(s) Are You Covering?
The topics you cover in your user interviews can affect the number of participants you need. To get more detailed insights, you might need to have more interviews, or ask more thorough questions. The broader your scope, the more participants you need to get all the insights you need. Remember, the goal is saturation: to cover all bases of the user experience. If you are trying to cover a lot of different topics, it will take more user interview participants to give you the data you need.
For comparison, imagine asking your users to test a new feature of an app compared to testing the entire app. They are two entirely different focuses. The scope for one is very honed in, while the other is zoomed out to the bigger picture. What you ask your users to focus on will dictate the type of feedback you receive.
Don’t expect the world if you only ask about a blade of grass. Likewise, don’t expect detailed feedback on the blade of grass if you’re asking about the entire world. Get your perspective straight and immediately put the user on the same page as you.
Population Diversity
If you’re trying to understand the needs of different user groups, you might need to conduct more user interviews. Your target group(s) and the diversity within that group also affects your ability to get all the necessary information.
While this is similar to the scope of your topics, population diversity mostly refers to how different your target users are from each other. It’s not just about the number of people in that demographic, but also the psychological makeup and the various personas and personalities that you have set as your target audience.
You will have to do separate qualitative research to unlock your target audience – who is using your service and why? These people will give the best feedback as these are the users who will actually be using your service. That’s not to say that people outside your target audience won’t have quality advice or feedback. Quite the contrary, they may bring attention to issues that might otherwise have been missed. But the most beneficial information will come from the people who will eventually be interacting with your user interface.
The Number of Participants Also Depends on the Experience of the Researcher
To conduct great research is a skill. Like any skill, it can be developed over time and with more experience. For example, when interviewing users, you want to make them feel comfortable. You need to ask the right questions at the right time in the right way. Depending on your team’s experience and skills, they may need to take some practice runs before they start getting quality data from user interviews.
One of the other things to consider is how good the note-taker is. If you aren’t recording the interview, you have to rely on notes made either during or after the interview. This type of notetaking can lose critical information. tl;dv is one of the best voice of the customer tools. You don’t need to hastily scribble down notes. Instead, you can use tl;dv’s note taker for Google Meet or the equivalent Zoom note taker and review the footage rather than go on memory.
tl;dr
To sum up, user interview saturation usually happens around the 5th interview. This number is set to differ based on your team’s experience, the population diversity, the scope of your research topics, and whether you’re using an interview recording software specifically designed with UX research in mind – like tl;dv!
Keep in mind, user interviews are just one type of research. They’re great for learning about user needs and opinions, but they shouldn’t be your only data source. Be sure to combine user interviews with other research methods like surveys, usability testing, and analytics to get a well-rounded understanding of your userbase.
If you’re still trying to work out how many user interviews you should do, it’s time to make a plan:
- Set your objectives for the research. What do you want to find out?
- Download tl;dv so you can record your sessions, rewatch them, take notes, tag your colleagues at relevant times, and much more.
- Set your scope: are you focused on one small thing, or a more general overview? Decide early.
- Choose users that are predominantly from your target audience.
- Make sure you make the user feel comfortable, assured, and at ease.
- Ask the right questions.
- Run your user interviews in rounds, fixing the issues raised by the initial users before interviewing the next batch.
If you follow these steps, you should naturally find the right number of user interviews for you. Good luck with your UX research!
