Today is an important day in the User Research calendar – World Usability Day (WUD) 2023. Also known as international ‘Make Things Easier Day’, WUD is an annual day of promotion for worldwide usability across things like engineering and design, to make things work better for all users!

As a specialist recruitment company for user research and testing, at People for Research (PFR), improving usability is at the heart of everything that we do.

From product to prototype testing, trialling new websites, platforms and much more, we help clients conduct user research with participants of all kinds to help improve their products and services for every user. However, as is the case with any research study, making sure you have the right sample size for the type of research that you are conducting is crucial to the validity of the insights you are hoping to gather.

📏Why size does matter

As the saying goes: size isn’t everything. But while this may be the case for many things, in user research and testing, we think it makes a real difference. In fact, when it comes to conducting effective research, having the correct number of participants can make or break your study. Get it wrong and you could risk skewing your results.

From doing a quick Google search or reading up on related blogs, you may have seen that researching with five participants is usually a good enough number to aim for. While this may be true for certain research studies, user research is not a ‘one-size-fits-all’ process.

What is a sample?

Essentially, a sample refers to a part of the population.

This might be a handful of people who belong to a certain demographic, for example, nationality or age, or those of a certain skillset, and is influenced by the objective of your research.

What determines the size of a sample?

While there’s no hard or fast rule as to the specific number of participants you should be testing with, there are some recommended sample-size thresholds to aim for. These are determined by the type of study that you’re looking to conduct, the amount of information you’re hoping to gather and is usually characterised by what is called ‘qualitative’ or ‘quantitative’ research.

Qualitative research refers to the collection of subjective data that cannot be measured numerically, such as individual opinions, thoughts, feelings or behaviours. This type of research allows the researcher to delve deeper into an individual’s pain points and gather fresh, often unexpected insights.

Quantitative research on the other hand is more interested in gathering objective data, for example, about a set number of people who do something. To put it simply, qualitative research is expressed in words, whereas quantitative research is characterised by numbers.

With these in mind, it’s best to identify which type of research will work best for you in securing the insights that you need – subjective or objective – before settling on a particular methodology for your study.

🧑‍🤝‍🧑 How many participants do I need for my study?

When conducting qualitative research, it’s best to aim for between four and 15 participants, or less than 20, as put by Mira Crouch and Heather McKenzie in ‘The logic of small samples in interview-based.’

As qualitative research is interested in subjective responses, researching with a smaller group of participants will help to “facilitate a close association with the respondents and enhance the validity of fine-grained, in-depth [research] inquiry,” they add.

Alternatively, if you’re conducting quantitative research, then researching with a minimum of 40 participants would help you secure the insights that you need.

As a rule of thumb, quantitative studies require four times as many users as qualitative research studies. This is because quantitative studies can be generalised to the whole population and so, require a higher volume of participants in order to smooth over individual variabilities in favour of an overall average.

Of course, the number of people you invite to partake in your research is up to you, but researching within the recommended sample sizes should secure you the results that you need.

🗒️ Examples of research methods

To help you visualise these research types more clearly, here are some of the different methods that you can approach when embarking on qualitative or quantitative research.

Qualitative research methods:

▪️ Interviews
▪️ Focus groups
▪️ Diary studies

Quantitative research methods:

▪️ Surveys
▪️ Treejacks
▪️ Card sorts

To delve into some of these research methods a little deeper, if you’re looking to conduct high-volume, quantitative research about a particular activity or subject, then opting for a survey-style research method would be the most effective approach for your study.

This might be a satisfaction survey for customers of a particular product with simple, one-to-five scale questions for participants to answer in as little as five minutes. This would allow you to reach a large number of people and obtain a high volume of data to assist you in your research.

Alternatively, if you wanted to get detailed, qualitative insights, for example, individual feedback on the usability of a website, then we recommend hosting short, online or face to face sessions with a smaller number of participants.

Here, you might test with a mix of 10 people of different ages and digital abilities to obtain a wide range of subjective feedback that will help towards making your product or service more usable!

Of course, that’s not to say that some research methodologies cannot be used for both qualitative and quantitative research studies, or even both together. These are just some of the many approaches you can take when embarking on user research and testing of your own.

If you are looking to conduct research and need help or advice with your study, why not get in touch or drop us an email at: info@peopleforresearch.co.uk.

Tom Vaughan, Community Marketing Assistant

If you would like to find out more about our in-house participant recruitment service for user research or usability testing get in touch on 0117 921 0008 or info@peopleforresearch.co.uk.

At People for Research, we recruit participants for UX and usability testing and market research. We work with award winning UX agencies across the UK and partner up with a number of end clients who are leading the way with in-house user experience and insight.