Research Methods: Participant Screening

Michael Brown

Screening Checkpoint Image

Photo by Graham Ruttan on Unsplash

A vital but often overlooked part of running effective research is screening participants to make sure you run interviews, surveys, prototype testing, workshops etc. with the best people to get the insights you need.

What is participant screening?

Basically, screening means ensuring the people who participate in your research are the right people to provide valuable insights. Screening is most often done via specific details in your call for participants or a screening questionnaire that participants must complete before you select them to take part. There might be simple inclusion criteria, such as an age limit, or you might gather more complex data to ensure your participants are from varied backgrounds or geographic regions.

The key question to consider when deciding who to include in your research is - will this characteristic affect the results? A person's gender may be irrelevant, but their responses and reactions could be significantly affected by age. Might location or job role make a difference to their attitudes and responses? If you're asking about particular experience, for example, moving house, you might want to specify how recent that experience must be - someone who last moved twenty years ago will have a very different set of responses to someone who moved last year. Think carefully about the type of person you are interested in - your participants should reflect that person as closely as possible.

How selective should you be?

Of course, participant recruitment can be tricky and you might not always get exactly who you want, so you should consider the effect your criteria will have on your ability to find enough participants and run rigorous, useful research.  

If you think you’ll struggle to get enough participants to draw reliable conclusions, it doesn’t make sense to have overly restrictive criteria.

On the other hand, if you're likely to have more potential participants than you are able to include, stricter screening will keep numbers under control and help get the most value from your research.

You also need to consider the risk/cost of involving participants that aren’t quite what you're looking for. For example, if you're running a quantitative survey, a few extra participants that aren’t ideally suited only really costs you a bit of time in data analysis. However, if you are running a face to face workshop an unsuitable participant at best reduces the space you have for others and at worst interferes with the focus and thus value of the entire workshop.

When to screen?

Another point to consider is when in the participant recruitment process you should screen out potential participants. If you screen too early you may discourage any participation by being too prescriptive in initial invitations to participate; too late and you're frustrating those who get screened out after spending time engaging with the process.

I find it best to screen early when performing one-off research to minimise participant frustration.

So in these situations I’ll include screening information in initial invitations or participant information provided before people have to get in contact with me. However, if you’re performing a series of studies in a related area, screening later can give you an opportunity to build up a panel of patients for future research, making sure those who have been screened out will have another chance to participate at a future date.

Screening and bias

In the same way that your recruitment method, study design and analysis can introduce bias into your research, screening can too. It’s important to think about why you're including any screening criteria and how these restrictions on participation could distort the results of the researcher. Unjustified geographic restrictions, for example, could mean your findings represent a local situation rather than a universal experience that affects all users.

Screening is a vital tool for getting the best insights from research but you must carefully consider why you are using each separate screening criterion and how it’s going to influence your recruitment, running the study, the results and recommendations you will produce.