Marketing & Innovation

The learning curve of qualitative studies

The learning curve that governs qualitative marketing studies is pivotal if you want to avoid ending up with mountains of useless data. What’s more, the kind of data produced by marketing studies is unstructured and complex. Gathering too much of it will also inevitably lead to soaring costs. Our simple methodology based on the experience curve of qualitative studies is a good starting point for making the most of these studies. What’s more, it’s a good means of improving effectiveness.

The Learning Curve of Qualitative Studies

Qualitative studies
After 10 to 12 interviews, insights derived from your interviews will plateau. This is when the qualitative marketing studies experience curve has been reached.

This method is straightforward. I owe it to my erstwhile marketing teacher, Pierre-Louis Dubois, a reference in the field of market research and the author of many marketing books. This methodology is all about effectuation.

Qualitative Studies and the Effectuation Principle

Be it for qualitative marketing studies, or in business in general, one must become familiar with the principle of effectuation. One could sum this notion up in just a few words: “The right effort for the right result, no more, no less.”

Common Sense and Qualitative Marketing Research

First of all, one must point out that the literature in this field is fairly confusing. Some authors recommend sampling strategies very similar to quantitative sampling strategies (Frisch, 1999), others aren’t quite sure and will tell you “it depends” (Quinn Patton, 2002, Qualitative research evaluation & methods), and others avoid answering the question altogether (Giannelloni and Vernette 2017).

It would seem that there is a space here for some down-to-earth commonsense for professionals wishing to do things right without giving in to hyperbolic methodological madness.

Qualitative studies
Because of the learning curve, we always aim for 12 interviews (10 when that’s not possible), dividing up the audience for our qualitative study to maximise our results. No need to organise hundreds of interviews, despite what some marketing pundits are suggesting.

Step one in qualitative studies

The first thing that strikes me when I see the work of students (but also that of some professionals) is that most of the time, they are off to a very bad and uncertain start. 

More often than not, they fail to understand the requirement for an initial level of investigation that could save them time and effort. Expert interviews, for instance. Be they internal or external SMEs, or both). No need to talk about sampling at this stage. The aim is different. You’re merely trying to make sense of a very fuzzy picture.

Qualitative studies
A good starting point for qualitative studies is to start with expert interview. What about starting with those who have written books on whatever subject you are researching?

Phase one of a qualitative study consists in a non-directive survey. You’ll start with a few assumptions and a list of questions that you’ll refine as you go along. This is not an in-depth questionnaire per se. 

By definition, you’re not an expert in the field that you are researching and you need to understand it beforehand. Desk research and expert interviews  are a sound starting point. This will help you polish your recommendations to your clients or your business partners. The more diverse these experts, the more valuable their insights.

Insights derived from such expert interviews will help you improve your understanding of the field of your research. Such insights will also help you hone your assumptions before you launch your qualitative study. Knowing what to search makes up for 50% of the success of your survey. 

Too many professionals ignore that first stage. It’s a shame because it’s also one of the most rewarding. It will, eventually, ensure you save time and effort and will yield better results.

By the way, with this initial phase, you will be in touch with various experts. These connections might prove useful in the future, you never know.

In-depth Qualitative Studies 

Time and time again, I was able to verify in the field what I’d learned from my time in business school. Studies always follow more or less the same pattern. This isn’t rocket science, it’s merely what I derived from experience. 

After the initial desk research and expert interview stages, you can then go out and interview larger samples. It’s not necessary to interview more than 10 to 12 people. You may interview more if you wish, but be aware that this will not yield many more insights. 

The Learning Curve in Qualitative Research

This is known as the “learning curve”. I haven’t found any scientific evidence for it, apart from the lectures I attended when I was at school, but I’ve been able to confirm these figures almost every time I’ve had to carry out an in-depth interview guide in the field. It always worked for me. Whatever the subject. The learning curve always peaks after 10 interviews, sometimes 11 or 12. Most of the time after the 12th interview. Beyond that, there’s no point in contacting more interviewees.

There is one proviso to that, though. Your interview guide must be well written and you must listen carefully to your interviewees. What this means is that your interview guide must be the same for all. That there is no bias in this guide. Lastly, it implies that your questions must be consistent throughout your interviews.

Beyond this qualitative study process, you will have to resort to a quantitative phase to gain a deeper understanding of your subject.

Sampling interviewees

I recommend you divide the number of people surveyed (let’s assume there are 12 of them) into as many subsets as possible in order to draw conclusions for each small subset. You will be able to quantify each of these subsets with your subsequent quantitative survey. You don’t need to make these subsets representative. But you need to have enough of them to gather consistent points of view.

Once again, no rocket science here, merely field experience. Should you interview 12 times the same kind of people, the insights you will derive from these interviews will be unbalanced.

What you want to do in the in-depth interview phase is to bring as many points of view as possible from the 12 you’ve collected, to bring different perspectives into your research. For instance (in B2B) 3 employees for the internal view, 6 buyers from 2 different subgroups for the external view and 3 resellers.

[Note that the same applies to B2C, replace “buyers” with “consumers” and resellers with retailers, for example].

Sample size for qualitative marketing research

If you need more insights, bringing in other subsets and expanding your sample beyond the limit of 12 might be a good idea. That is if you think you’ll have enough time to conduct these interviews, make the transcriptions, analyse the results, and that there will be a benefit for you. In any case, if the insights you are getting are repetitive, put an end to that interviewing process to save time and money.

Finally, remember that qualitative studies only provide insights. Such insights will have to be verified and quantified at a later stage. They should never be taken at face value. In fact, they are often used as the basis for the forthcoming quantitative study.

Customer Interviews

With regard to customer interviews, one will be essentially looking for very precise, in-depth customer insights on a subject that isn’t necessarily quantifiable. Besides, when dealing with hard-to-sell products or services (aka complex selling), customers are by definition in short supply. Samples are therefore too small to conduct quantitative interviews. In this case, statistics won’t help. Qualitative studies are, in that case, a no-brainer. 

Qualitative studies
Qualitative studies can also be used for customer feedback in order to improve customer experience

Beyond that, the methodology is pretty much the same. The content of your interview guide, however, will be very different. It will be all about the relationship between your customer and the business and/or its representatives. Each case is unique, there are no one-size-fits all interview guide for customer interviews.

The Why and the How

First of all, you need to define why you are interviewing your customers. Is it about measuring product or service quality or product-market fit, assessing relationship quality, understanding customer issues, or anticipating a change in market needs? Unless it is far more specific. In the case of the launch of a new offer, product, or service, for instance.

You will also need to know how to decrypt when customers are paying lip service to your questions. Namely when a sales rep is facing her customer during the interview. Buyers may not always feel comfortable when criticising vendors openly.

In this case, customers will most probably refrain from opening their kimonos, in order to retain their bargaining power. 

Thus, you’ll also need to decode your customers’ words to understand false and true arguments. Reading between the lines is a must in that case. Cross-checking information will also be necessary.

In other words, it’s quite difficult to carry out this type of survey if you’re on the vendor’s side, to maintain enough neutrality when you are being criticised. Frequently however, customers’ strong feelings are the most valuable and useful form of feedback if you want to improve your offer and service quality.

Yann Gourvennec
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Yann Gourvennec

Yann Gourvennec created in 1996. He is a speaker and author of 6 books. In 2014 he went from intrapreneur to entrepreneur, when he created his digital marketing agency. ———————————————————— Yann Gourvennec a créé en 1996. Il est conférencier et auteur de 6 livres. En 2014, il est passé d'intrapreneur à entrepreneur en créant son agence de marketing numérique. More »
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