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How Many User Interviews (Participants) Should You Do For Your UX Research?

User interviews are a great way to gain valuable insights and ideas from your users while building relationships. But when it comes to conducting the actual interviews, many researchers get stuck at “How many user interviews do I have to conduct to get the best results?”. It is normal for you as a researcher to wonder how many interviews are enough. Like with many other things in research, it depends. This article will take you through the ideal target number of participants and how to determine the number of participants you need for your UX research.Β 

Knowing the number of users or participants to interview helps you get the best insights and helps you save on expenditure and time. Money goes into research, and it won’t be ideal for spending money on extra participants when you don’t need anymore. Still, on the other side, your research will be lacking if you have fewer participants than you actually need. 

How Many User Interviews (Participants) Should You Do For Your UX Research?

Conducting the User Interview

The golden number when it comes to user interview participants is five (5). Jakob Nielsen and Tom Landauer, founders of the Nielsen Norman Group, arrived at the number of five. So, if you are looking for a single number for just how many interviews are enough, it would be this, but be careful because it is definitely conclusive for every single user research. In their research, the two user experience researchers found that interviewing five users helped gain about 85% of the insights you need for your research on usability. Their research revealed that additional participants gave less and fewer insights. After 5 participants, you start to get diminishing returns on each user interview. So, it makes sense to start with five as a default number. However, five participants don’t always give the best value. Understanding the difference between uncovering issues and understanding users’ experiences are two different things that will help you appreciate the fact that five users aren’t enough for your research.

A few ideas on how to customize this number for yourself would be to start with 5 participants, then add up to five additional participants based on the complexity of issues and topics you want to uncover, and multiply the number you get by the number of personas you are interviewing based on your user research goals and objectives. Lastly, add one or two participants if your team is new or needs to get the process right. 

While it is easy to conclude that you can get the majority of the issues you need as well as some insights with only five interviews and five participants, it is not nearly as easy to tell you the exact number you need for your own research. Unfortunately, there is little agreement on this matter in the UX research community. Various research has come out with varying numbers, which could mean little to any researcher since they are widely different in each instance. This is why we have outlined some factors in the next section to help you decide for yourself just how many user participants you need for your UX research.  

In a nutshell

In a nutshell, just how many interviews are enough to conduct for your research depends on your research goals and objectives? For example, if you want to get user feedback on a new feature, you might only need a handful of interviews. But if you’re trying to understand user behavior or uncover user needs, you might need many more.

The ideal target number of participants for a user interview is 6-8. This allows you to get a good mix of perspectives and opinions without spending too much time conducting interviews. Of course, there are always exceptions to this rule. For example, if you’re looking for very specific insights or feedback, you might need fewer or more participants.

How to Determine How Many Interviews to Conduct

How to Prepare for a User Research Interview

Go After Saturation (Seek Diminishing Returns)

It may be difficult to tell how many users you need for your interviews, but it is quite better to tell when you are approaching saturation. And that is what you should aim for; saturation. If you want just how many interviews are enough, the truth is, you can uncover the majority of issues from a few users, and you could even uncover all issues after three interviews. For this reason, instead of looking for a golden number to interview, look for golden insights. You can tone down on additional users as you approach the goal or objectives you set for your research project. 

Your number one job as a researcher 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 need to interview each participant as much as you need to. Start with open-ended questions that trigger them to go both broad and deep about their motivations, habits, and how they get things done on a daily basis. 

Seek details about what they do and their feelings about various issues surrounding their life. Record each session with tl;dv and review them after each day of the interview ends. As you discuss with your team, it makes it easier to identify patterns, and eventually, you will be able to tell when you are no longer gaining enough new information or no new insights at all. 

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? This is because, at a certain point, you begin to gain less and less new information until you reach saturation. When your sessions start to feel very repetitive, with the same opinions and information, it may be time to end your interviews.  

There is No Magic Number

As already indicated, there is no magic number, unfortunately. But that doesn’t have to be a bad thing. Research, and particularly user interviews, are highly subjective. That means you cannot tell how many users you need to gain your insights. It could be two, and it could be 63. So instead of focusing on a golden number, each UX researcher should focus on their project and its specific requirements and needs; there lies the number of participants that you need. 

Here are researches that came out with different results for the ideal number.

  • Nielsen Norman recommends that five usability test participants be enough per interview round.
  • Mark Mason reviewed 560 qualitative research papers in 2010 and recommended that participants should be between 1 and 95, which is a vast gap, making the recommendation less valuable. However, the average from his research was 31, but it came with a large standard deviation, of course. 
  • In an ethnographic study, Greg Guest and Co arrived at 12 interviews giving 97% of research codes while 94% of research codes came from the very first 6 of the participants. This study is similar to the findings of the NN Group. 

The key lesson here is to work to achieve your objectives and get as many or fewer users as you need to achieve them. 

What Topic (s) Are You Covering?

More detailed insights will require more interviews. The topics you want to cover in your interviews can affect the number of participants you need. The broader your scope, the more participants you need to get all the good insights you need. Remember saturation? Good. If your topics are many, it will take longer and more users to reach that saturation level.

An example would be testing a feature compared to testing the entire app. The scope is not the same. If you are performing discovery interviews, your scope is extensive, and you may have to talk to people. For example, suppose you are developing a healthcare application and need to know what people think about healthcare, their problems, and challenges with their healthcare. In that case, that will bring in very diverse responses, and it would take time to exhaust every bit of detail within that scope. 

Population Diversity

If you’re trying to understand the needs of different user groups, you might need more interviews. Your target group (s) and the diversity within the group also affects when you approach diminishing returns and when you achieve saturation. This is important and similar to the scope of your topics. But with the population, we refer to how different your target users are from each other. But your population diversity is not just about the number of people in that demographic but also about the psychological makeup and the various personas you have dreamed of for your project. 

To get accurate here, you need to know your personas well. You could have separate qualitative research to get the personas right or do secondary research to make sure you are proceeding on the right path. 

The Number Of Participants Also Depends On The Experience Of The Researcher

Research takes specific skills that are only harnessed over time and experience. For example, interviewing users, making them feel comfortable, and asking the right questions at the right time in the right way doesn’t come by chance. And depending on your team’s experience and skills, they may need one or two extra participants to practice before taking on the entirety of the interview sessions.Β 

Another layer that comes here is how good is the notetaker? Are you recording the session? Remember that recording every session is advisable and tl;dv can help you achieve that perfectly, along with taking notes and generating transcripts for your interviews. 

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 or the product in general, 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.

To sum it up, user interview saturation usually happens around the 5th interview. Still, this number will differ based on your team’s experience, the population diversity, and the scope of your research topics. The best way to determine how many user interviews you need is to

Remember, 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 users.

Conclusion

There are several factors to consider when deciding the number of participants for your research. Regardless of the actual number you choose, you need to have good planning in place, ask the right questions in the right way and always follow up with questions for more details. Starting on the right foot is the only way to succeed with your user research, which involves setting the right goals and objectives. Start small (probably 5) and add more participants as you conduct more interviews and analyze the data that you are getting. Remember to record your sessions for analyses later with tl;dv!