You’ll find a lot of information and debate about sampling issues in qualitative research: discussions over ‘random’ or ‘purposeful’ sampling, the merits and pitfalls of ubiquitous ‘snowball’ sampling, and unending questions about sample size and saturation. I’m actually going to address most of these in the next blog post, but wanted to paradoxically start by looking at recruitment. What’s the difference, and why think about recruitment strategies before sampling?
Well, I’d argue that the two have to be considered together, but recruitment tends to be a bit of an afterthought and is so rarely detailed in journal articles (Arcury and Quandt 1999) I feel it merits its own post. In fact, there is a great ONS document about sampling, but it only has one sentence on advice for respondent recruitment: “The method of respondent recruitment and its effectiveness is also an important part of the sampling strategy”. Indeed!
When we talk about recruitment, we are considering the way we actually go out and ask people to take part in a research study. The sample frame is how we choose what groups of people and how many to approach, but there are huge practical problems in implementing our chosen sampling method that can be dealt with by writing a comprehensive recruitment strategy.
This might sound a bit dull, but it’s actually kind of fun – and the creation of such a strategy for your qualitative research project is a really good thought exercise, helping you plan and later acknowledge shortcomings in what actually happened. Essentially, think of this process as how you will market and advertise your research project to potential participants.
Sometimes there is a shifting dynamic between sampling and recruitment. Say we are doing random sampling from numbers in a phone book, a classic ‘random’ technique. The sampling process is the selection of x number of phone numbers to call. The recruitment is the actually calling and asking someone to take part in the research. Now, obviously not everyone is going to answer the phone, or want to answer any questions. So you then have a list of recruited people, which you might actually want to sample from again to make a representative sample. If you found out everyone that answered the phone was retired and over 60, but you wanted a wider age profile, you will need to refactor from your recruited sample.
But let’s think about this again. Why could it be that everyone who consented to take part in our study was retired? Well, we used numbers from the phone book, and called during the day. What effect might this have? Numbers in the phone book tend to be people who have been resident in one place for a long time, many students and young people just have mobiles, and if we call during the day, we will not get answers from most people who work. This illustrates the importance of carefully considering the recruitment strategy: although we chose a good random sampling technique, our strategy of making phone calls during the day has already scuppered our plans.
How about another example: recruitment through a poster advertising the study. Many qualitative studies aren’t looking for very large number of respondents, but are targeting a very specific sample. In this example, maybe it’s people who have visited their doctor in the last 6 months. Sounds like a poster in the waiting room of the local GP surgery would work well. What are the obvious limitations here?
First of all, people who see the poster will probably have visited the GP (since they are in that location), however, it actually only would recruit people who are currently receiving treatment. People who had been in the previous 6 months but didn’t need to go back again, or had such a horrible experience they never returned, will not see our poster and don’t have a chance to be recruited. Both of these will skew the sample of respondents in different ways.
In some ways this is inevitable. Whichever sampling technique and recruitment strategy we adopt, some people will not hear about the study or want to take part. However, it is important to be conscious of not just who is being sampled, but who is left out, and the likely effect this has on our sample and consequently our findings. For example our approach here probably means we oversample people who have chronic conditions requiring frequent treatment, and undersample people who hate their doctor. It’s not necessarily a disaster, but just like making a reflexivity statement about our own biases, we must be forthright about the sampling limitations and consider them when analysing and writing conclusions.
For these reasons, it’s often desirable to have multiple and complementary recruitment strategies, so that one makes up for deficiencies in the other. So a poster in the waiting room is great, but maybe we can get a list of everyone registered at the surgery, so we can also contact people not currently seeking treatment. This would be wonderful, but in the real world, we might hit problems with the surgery not being interested in the study, not able to release that information for confidentiality reasons, and the huge extra time such a process would require.
That’s why I see a recruitment strategy as a practical battle plan that tries to consider the limitations and realities of engaging with the real world. You can also start considering seemingly small things that can have a huge impact on successful recruitment:
• The design of the poster
• The wording of invitation letters
• The time of day you make contact (not just by phone, but don’t e-mail first thing on a Monday morning!)
• Any incentives, and how appropriate they are
• Data protection issues
• Winning the support of ‘gatekeepers’ who control access to your sample
• Cost (especially if you are printing hundreds of letters of flyers)
• Time and effort required to find each respondent
• And many more…
For a more detailed discussion, there’s a great article by Newington and Metcalfe (2014) specifically on influencing factors for recruitment in qualitative research.
Finally, I want to reiterate the importance of trying to record who has not been recruited and why. If you are directly contacting a few dozen respondents by phone or e-mail, this is easy to keep track of: you know exactly who has declined or not responded, likely reasons why and probably some demographic details.
However, think about the poster example. Here, we will be lucky if 1% of people that come through the surgery contact us to take part in the study. Think through these classic marketing stages: they have to see the poster, think it’s relevant to them, want to engage, and then reach out to contact you. There will be huge losses at each of those stages, and you don’t know who these people are or why they didn’t take part. This makes it very difficult in this kind of study to know the bias of your final sample: we can guess (busy people, those who aren’t interested in research) but we don’t know for sure.
Response rates vary greatly by method: by post 25% is really good, direct contact much higher, posters and flyers below 10%. However, you can improve these rates with careful planning, by considering carefully who will engage and why, and making it a good prospect to take part: describe the aims of the research, compensate time, and explain the proposed benefits. But you also need to take an ethical approach, don’t coerce, and make promises you can’t keep. Check out the recruitment guidelines drawn up by the Association for Qualitative Research.
My personal experience tells me that most people who engage with qualitative research are lovely! They want to help if they can, and love an opportunity to talk about themselves and have their voice heard. Just be aware of what kinds of people end up being your respondents, and make sure you acknowledge the possibility of hidden voices from people who don’t engage for their own reasons.
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