Sabine Caillaud

Nikos Kalampalikis

Marjolaine Doumergue

Designing focus groups

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Introduction

Newcomers to focus groups are often bewildered by the different and sometimes contradictory advice in the literature about dos and don'ts regarding the use of this method. This state of affairs is best explained by the method's history. The origins of focus groups are diverse, and include, at the least, mass media and communication research, sociology and social psychology, clinical psychology and marketing research [START_REF] Stewart | Focus Groups. Theory and Practice[END_REF]. While this chapter does not claim to provide an exhaustive review of research on the topic, it seeks to offer some rules of thumb for planning and designing focus groups. It begins with a brief historical overview outlining the epistemological and disciplinary assumptions that have tended to guide focus group research. It then centres on a definition of focus groups as a method that explicitly uses social interactions, both as a way to produce data and as data itself, illustrating this with a study on disability. Drawing on this social-interaction-centred definition of focus groups, the chapter goes on to examine concrete issues regarding focus group design: the composition of the group, its physical organization (including the recent possibility of online discussions), the role of the moderator, what to ask, and how to analyse the data. The overall aim is to provide readers with the main methodological questions that should guide their choices when designing a focus group study.

Focus groups: a multi-branched history

The trajectory of focus groups in qualitative research begins in the socio-political context of WWII and the post-war period, marked by the growing impact of mass communication and propaganda. Despite some evidence of the previous use of group interviews by [START_REF] Bogardus | The group interview[END_REF], the method was initially developed at the entry of the United States in WWII by Merton and Lazarsfeld (Merton, 1987), originally taking the name 'focused interview'. Lazarsfeld and Merton collaborated in a commission, which later became the Office of War Information, to measure the effects of radio programmes of a moral nature broadcast to the American public. [START_REF] Merton | The focused interview and focus groups: continuities and discontinuities[END_REF] recalls that his first encounter with Lazarsfeld gave rise to the 'invention' of a specific type of interview.

Merton and Lazarsfeld met for the first time in November 1941 when both were invited to a guest dinner. But rather than attending the dinner, Lazarsfeld dragged Merton to a live experiment that was part of a research programme he was conducting. In a radio recording studio, a dozen subjects seated in two or three rows were listening to a broadcast. When it evoked positive feelings, they were asked to press a green button, or a red button for negative feelings. Their answers were recorded by a polygraph-type instrument. In the absence of a one-way mirror, the two sociologists found an unobtrusive place in the room to observe the experiment. After the radio programme, the experimenter asked the participants to explain their reactions. This was the first time Merton had observed this type of collective experiment, and he was particularly fascinated by the lively debate generated by the confrontation between participants. Yet his practice in individual interviewing made him critical of how the experimenter conducted the interview. Throughout the experiment, Merton constantly passed notes to Lazarsfeld with comments regarding the overly directive style of the moderator, the lack of focus on specific individual and collective reactions, the failure to take spontaneity into consideration, and so on. At the end of the evening, Lazarsfeld, seeing Merton's keen interest in the method, asked if he wanted to be involved in how the interview should be conducted in the next group planned for the experiment. The work of these two sociologists was fundamental in developing the precursor concept of focus groups.

While the 'invention' of focus groups has long been attributed to Merton and his collaborators, this term was never used at the inception of their work. Rather, they employed the term 'focused interview' to emphasize that the interview technique, suitable both for individuals and for groups, relies on a concrete situation (i.e. the 'focus') participants have been involved in (e.g. a radio programme they have listened to, a film they have seen, a book they have read, etc.) to foster discourse about their subjective experience of it [START_REF] Merton | The focused interview[END_REF]. At that time, this technique was part of a toolbox of methods combining experimental and qualitative data: the focused interview was used to identify potential elements that may have led to observed effects and thus to develop new hypotheses that were then tested in experiments [START_REF] Merton | The focused interview and focus groups: continuities and discontinuities[END_REF]. Last but not least, Merton did not sharply distinguish between individual and group interviews, although he considered that group interviews may elicit a broader range of responses stimulated by social interactions. However, he also considered that this interaction might 'contaminate' individual responses [START_REF] Merton | The focused interview and focus groups: continuities and discontinuities[END_REF][START_REF] Barbour | Doing Focus Groups[END_REF].

Later, with the influence of the behaviourist model, the use of this technique would almost completely disappear in the social sciences for more than 15 years. But in marketing research, Merton's work did not go unnoticed: it provided an opportunity to observe the consumer in person and to access their attitudes and motivations via a user-friendly method. The method also became a mainstay of broadcasting and public opinion research in the post-war period [START_REF] Kidd | Getting the Focus and the Group: Enhancing Analytical Rigor in Focus Group Research[END_REF]. Marketing studies tap into the techniques developed in media and communication research, which are well adapted for situating attitudes and opinions, as well as into the group techniques developed by clinical psychology to access subtler aspects such as motivations. As a result, numerous manuals were produced that disseminated sometimes contradictory generalities on how to conduct focus groups, for the most part overlooking the researcher's interests that predetermine why the method is used [START_REF] Barbour | Doing Focus Groups[END_REF]. In parallel, in clinical psychology, the technique was used with the assumption that interactions between participants should facilitate the individual's treatment process, putting the emphasis on interactive group discussions and the spontaneous expression of deep thoughts and feelings [START_REF] Stewart | Focus Groups. Theory and Practice[END_REF]. Other uses of focus groups were developed in the framework of sociological intervention and community development and participatory approaches [START_REF] Barbour | Doing Focus Groups[END_REF]. Thus, the origins of focus groups are numerous; as a consequence, guidelines on how to conduct them vary dramatically.

In the 1990s, with a return to qualitative methods in the social sciences, focus groups again began to be considered in their original disciplinary context [START_REF] Barbour | Developing focus group research: politics, theory and practice[END_REF][START_REF] Barbour | A New Era in Focus Group Research[END_REF]: in particular, in social psychology [START_REF] Flick | An introduction to qualitative research[END_REF][START_REF] Kalampalikis | Les focus groups, lieux d'ancrages[END_REF][START_REF] Kitzinger | Qu'est-ce que les focus groups?[END_REF]) and sociology [START_REF] Morgan | Focus groups: a new tool for qualitative research[END_REF]. In this context they were essentially seen as a qualitative method complementary to those existing up to that point. These diverse uses of focus groups considerably enriched the method, and although on the one hand this carries the risk of creating a heterogeneous melting-pot, on the other the lessons learned from the different domains potentially allow the researcher to pick the 'best technical ideas' from various fields according to the research aims (Goldman & McDonald, 1987, p. 3). So while in the field of marketing a one-size-fits-all approach has been developed, we argue for a reflexive approach in designing focus groups that incorporates the lessons learned through the multiple uses of the method.

Paradoxically, in various recent English-language publications, there is either no mention of Merton's seminal work or he simply appears as the 'inventor' of focus groups. Yet the ideas developed by Merton still structure some of the current debates regarding focus groups: that they should be systematically combined with quantitative methods to enhance validity, that content obtained during individual and group interviews should be compared, and that group interactions may contaminate an individual's opinion. However, by reconnecting with qualitative research, the method has undergone an epistemological shift concerning the way it approaches social interactions that has an influence on all these debates.

A focus on social interactions

Our starting point is a definition of focus groups as a method "that collects data through group interactions on a topic determined by the researcher" (Morgan, 1996, p. 130). In contrast to an ordinary discussion, the focus of the discussion is proposed by the researcher, and participants are explicitly informed about it [START_REF] Kitzinger | Qu'est-ce que les focus groups?[END_REF]. While other purposes can exist, the primary aim is research. One of the most important characteristics of focus groups is the explicit use of group interactions between participants [START_REF] Asbury | Overview of Focus Group Research[END_REF][START_REF] Barbour | Doing Focus Groups[END_REF][START_REF] Kitzinger | The methodology of Focus Groups: The importance of interaction between research participants[END_REF]. While during one-to-one interviews participants address their answers directly to the interviewer, during focus groups, participants are called on to interact with each other. The method capitalizes on this interaction within a group to elicit rich experiential data [START_REF] Asbury | Overview of Focus Group Research[END_REF][START_REF] Wilkinson | Focus groups in health research: Exploring the meanings of health and illness[END_REF]: participants explain their points of view, they share their feelings, they make arguments and counter-arguments to develop their ideas, they complete each other's thoughts, etc. These interactions facilitate types of discourses that are difficult to obtain in other contexts. They also place the focus on participants' points of view rather than exchanges with the researcher, making it a valuable method when working with vulnerable people [START_REF] Liamputtong | Focus Group Methodology[END_REF].

However, focus group studies differ in how and why they use group interactions [START_REF] Ruiz | Collective Production of Discourse: an Approach Based on the Qualitative School of Madrid[END_REF]: an individualistic approach considers that these interactions are valuable yet create potential bias that must be minimized by the moderator to gain insight into the 'real' opinion of each participant (a perspective close to that of Merton). According to this approach, focus group results are not considered as trustworthy or valid as results from individual interviews. In contrast, a group-based approach encourages group interactions, which are taken into account during the analysis in a constructivist perspective [START_REF] Kitzinger | The methodology of Focus Groups: The importance of interaction between research participants[END_REF][START_REF] Morgan | Focus Groups[END_REF][START_REF] Duggleby | What About Focus Group Interaction Data?[END_REF]. This approach (see also [START_REF] Ruiz | Collective Production of Discourse: an Approach Based on the Qualitative School of Madrid[END_REF] even considers focus groups as a means to investigate group discourse, rather than simply gathering the views and opinions of different individuals in a group context. It assumes that participants may say things that they would not have said in an individual interview. This position is consistent with a Lewinian perspective on groups, which considers that a whole is more than the sum of its parts [START_REF] Watts | More than the Sum of the Parts: Research methods in group interviewing[END_REF]. In this view, focus groups are conceived of as "simulations of social relations and social occasions, like conversation, public discussion and gossip, where meaning is produced and reproduced in everyday life" [START_REF] Lunt | Rethinking the Focus Group in Media and Communications Research[END_REF]. Group effects in this context are not considered to generate bias, but as both a source of data production and a result in itself, as these effects help to understand the group processes by which specific social meanings are reconstructed [START_REF] Morgan | Reconsidering the Role of Interaction in Analyzing and Reporting Focus Groups[END_REF].

An example from a psychosocial study illustrates how group interactions can be used both to support data production and to understand the group processes underlying the reconstruction of meaning. The study [START_REF] Caillaud | From one new law to (many) new practices? Multidisciplinary teams reconstructing the meaning of a new disability law[END_REF] sought to analyse how French health professionals implemented a new disability law in their professional practice. In France, child disabilities are assessed by multi-disciplinary teams of professionals (physicians, psychologists, teachers, etc.) who construct a tailored support programme (e.g. benefits, care, special education, etc.) on the basis of external experts' reports (from the physician, psychologist, teacher, etc.) without meeting the child. In 2005, a new law was passed inspired by World Health Organization (WHO) directives that view disability as a situation resulting from socio-psycho-biomedical factors. This new definition contrasts to the more strictly biomedical approach that French health professionals previously referred to for their assessments (Winance et al., 2007). Moreover, despite the existence of a national legal framework of reference, each regional institution can freely decide how to concretely apply the new law and conduct the assessment, opening the possibility for different implementation of the same law. The study aimed to understand how these teams of professionals deal with the tensions between the ideas in the new law incorporating a new model of disability and the pre-existing ideas previously in force regarding disabilities.

To this end, 10 focus groups (N= 65) consisting of multi-disciplinary teams in charge of child disability assessment were conducted in 10 French regions. We used natural groups (one existing team of professionals in each region), so that the processes of these teams could also be captured. The number of participants in a focus group varied from 4 to 13, reflecting local differences in the composition of the existing teams, as each region was free to decide which professionals should be involved. However, in each group there was at least one doctor and one psychologist. The focus groups took place in the room where the teams usually meet.

The focus groups were designed with the goal of stimulating group interactions. The moderator first introduced the discussion by briefly presenting the research aim and then explicitly invited participants to give their own point of view and to discuss together. In the first part of the discussion, groups were asked to discuss how an ideal team should work (e.g. what multi-disciplinary work should involve, how they should ideally manage their alterity, what elements are needed for conducting a good disability assessment, etc.). Asking their opinions about what constitutes ideal teamwork was expected to encourage debate between the participants. If instead we had asked the team to explain what their work involves (a factual question), we suspect that one team member would have answered the moderator directly. In the second part, groups were confronted with a fictitious case (inspired by previous real cases) in which the medical and psychological information were in contradiction: the medical report stated that the child had a visual impairment of less than 50%, whereas the psychological report indicated that this impairment was associated with psychological suffering, feelings of exclusion, and low self-esteem. This allowed an examination of the tensions between the old category-based model and the new global model of disability. On the sole basis of the medical report, the child would not be considered as disabled, whereas according to the new model, other elements (in this case, psychological information) should be taken into account in order to reach a conclusion. As this fictitious case was quite similar to the team's daily tasks, it offered the possibility of gaining insight into their practices and fostering interaction and debate: based on different (and sometimes divergent) information, they had to discuss a case in order to reach a consensus.

The focus groups (mean duration: 1h 45m) were recorded on video. The discussions were transcribed in full and coded according to five aspects (1-5 in Table 1). The codes were developed inductively and the analysis sought to outline how the group interactions and the content were interrelated. The table below summarizes the main findings.

Representations of disabilities and group dynamics

A medical approach (3 teams)

A case-by-case approach (4 teams)

A systemic approach (3 teams)

What is disability?

Disability is a medical category Disability is primarily a medical category, but there are some exceptions Disability is the result of a personenvironment interaction

How is disability evaluated?

Solely on the basis of medical elements

Depending on the level of impairment By gathering information from all professionals

Legitimacy granted to different experts

Medical knowledge is central, other types of knowledge are denied

The physician is the sole expert, but other points of view are also considered of interest Recognition of all relevant knowledge as expertise

Distribution of participation in the case

Physician talks 1.34 times more than the other team members Physician talks 1.49 times more than the other team members Similar contribution times from different team members

How contradictory points of view are managed

Some team members try to disagree in an implicit way ("I agree, but …")

If the impairment is not clear-cut medically, other professionals explicitly disagree with the physician and contradicting points of view are recognized Team members employ shared meaning categories (narratives) and ask numerous questions

The results revealed three different relational outcomes: i.e. representations of disability (1 & 2) were associated with three different group dynamics (3, 4, 5). For example, three of the teams took a medical approach (column 2): they considered the limitations of the new law In this excerpt, the physician makes it clear that the case they are discussing is not a physical impairment. He moves from "I think" (in my opinion) to "we decide" (we could encourage), demonstrating his central role. The other participants acknowledge this, with even the psychologist prefacing her comments with "Um yes" before mentioning that there may be doubts regarding the impairment ("we do not really know"), a point of view that is contradicted by the next participant who considers that the physician "has established" this, indicating that no discussion is possible. We found that this medical approach to disability was associated with a team dynamic marked by the supremacy of the medical viewpoint (in terms of the legitimacy granted to this expert and the physician's high participation) and that disagreements with this were only expressed in an implicit mode (e.g. "yes, but…") by the other team members.

As has been shown in other studies, focus groups offer the potential to jointly analyse the content and dynamics of team discussions [START_REF] Kidd | Getting the Focus and the Group: Enhancing Analytical Rigor in Focus Group Research[END_REF][START_REF] Caillaud | Focus groups and ecological practices: a psychosocial approach[END_REF]. Our study demonstrated that, despite the existence of a single law, the teams had different representations of disability, potentially leading to differences in treatment and access to assistance in France, depending on the dynamics of the local team. While the study did not allow conclusions about the opinions of individual team members, it provided clear answers on the way teams implemented the new law, which is more relevant in this case, as decisions regarding disabilities are taken collectively. Thus, we considered focus groups could be employed as a standalone method to provide sufficient and trustworthy findings, a position that differs from Merton's initial work.

How to plan focus groups

Points to keep in mind

There are some rules of thumb to consider before designing a focus group study. As mentioned, the design should encourage the flow of interactions between participants and 1 The interview was translated from French by the authors.

offer the most intense group dynamics possible. Moreover, the researcher should be mindful of the different reasons to foster group interactions for the specific research aim. Is the goal to produce rich experiential data (for example, with the purpose of preparing a relevant questionnaire/survey)? Or is it to analyse the social processes that sustain the co-construction of meaning? This may have important consequences as, in contrast to a one-to-one interview, two aspects can be more or less structured in a focus group discussion [START_REF] Morgan | Focus Groups[END_REF]: the content of the discussion (what participants talk about can be the focus to a greater or lesser degree), and the group dynamics (are participants free to interact, or does the moderator regulate participation?). In the example of our disability study, group dynamics were little directed as the research aim sought to capture the relational dynamics of each team of professionals (for another example, see [START_REF] Caillaud | How groups cope with collective responsibility for ecological problems: symbolic coping and collective emotions[END_REF]. Concerning the content, the focus group can be structured by asking more or fewer questions: if the aim is exploratory, just one question could be used to start the discussion. However, it should be noted that if both the content and the dynamics are strongly directed, this may result in a group interview that is rather poor in content (with participants addressing the moderator and providing successive, brief answers without interaction between participants).

Another issue that is important to consider before designing a focus group study is its potential integration in a larger research design that employs a triangulation approach (Flick, 2008). Using focus groups alongside other methods can help to delimit and clarify the research questions to be specifically answered by the focus group study [START_REF] Michell | Combining Focus Groups and interviews: Telling how it is; telling how it feels[END_REF][START_REF] Lambert | Combining individual interviews and focus groups to enhance data richness[END_REF][START_REF] Caillaud | Focus groups in triangulation contexts[END_REF].

Sampling and group composition

The first two crucial questions at the outset of designing a focus group involve the sample: Who to invite? Who to bring together? The first question can be answered by referring to the main principles of qualitative sampling developed in chapter 22. The choice of the sample should be guided by the main relevant aspects in relation to the topic being studied and that will potentially raise a range of experiences and perceptions [START_REF] Barbour | Doing Focus Groups[END_REF].

The second question involves group composition. In general, homogeneity is associated with greater compatibility and willingness to communicate in a group [START_REF] Stewart | Focus Groups. Theory and Practice[END_REF]: participants that share similarities are more confident and less afraid of disruptive conflicts, especially on sensitive topics [START_REF] Bloor | Focus Groups in Social Research[END_REF][START_REF] Hyde | The focus group method: Insights from focus group interviews on sexual health with adolescents[END_REF]. Actual or perceived discrepancies in status or power between participants may lead to the views of lower-status members to be silenced [START_REF] Michell | Combining Focus Groups and interviews: Telling how it is; telling how it feels[END_REF]. So a 'successful' group would consist of participants with a degree of homogeneity that provides a sufficient sense of commonality, allowing a degree of heterogeneity in terms of attitudes or perspectives to be expressed in an in-depth and insightful debate between participants [START_REF] Morgan | Conclusions: A call for further innovations in focus groups[END_REF]. However, the research question often determines the constitution of the group: in our disability study, the aim was to follow how professionals from different disciplines debate in order to evaluate cases, thus the groups were not homogeneous in terms of professional background. If our aim had been to determine how each type of professional engages with the new law, we would have conducted focus groups consisting of people with the same profession. Practical issues may also come into play: e.g. how do you bring together professionals from different regions? In addition, in workplace settings, as was the case in our disability study, existing hierarchical Authors' version : Caillaud, S., Kalampalikis, N. & Doumergue, M. (à paraitre). Designing Focus Groups. In U. Flick (Ed) The Sage Handbook of Qualitative Research Design. Sage relationships may impact what some participants are willing to share. While this was relevant to our study as it was one of our research questions, these existing relationships may also be perceived as threatening by some participants and reduce their participation [START_REF] Brannen | Work-family matters in the workplace: the use of focus groups in a study of a UK social services department[END_REF].

A further point to consider is that if the aim is to explore how one variable influences the content of the discourse, then at least two focus groups must be conducted for each modality of the variable in order to interpret the differences (e.g. 1 variable 'professional background' x 4 modalities {physicians, psychologists, teachers, other non-medical professionals} x 2 groups = 8 focus groups, see [START_REF] Asbury | Overview of Focus Group Research[END_REF]. Since focus groups are resource-demanding (in terms of recruitment of participants and transcription and analysis of the data), the number of comparisons planned has to remain reasonable [START_REF] Barbour | Doing Focus Groups[END_REF].

Small groups (4 to 8 participants) are recommended to generate in-depth debate or to investigate difficult topics [START_REF] Hopkins | Thinking Critically and Creatively about Focus Groups[END_REF][START_REF] Kounta | Sex work among female workers in the traditional mining sector in Maliresults from the ANRS-12339 Sanu Gundo cross-sectional study in 2015[END_REF]. The greater the participants' engagement with the topic, the smaller the group should be, as they will each want to their views in detail and share their feelings [START_REF] Morgan | Why Things (Sometimes) Go Wrong in Focus Groups[END_REF][START_REF] Bloor | Focus Groups in Social Research[END_REF]. If participants are numerous, they are tempted to start parallel discussions. While using groups of strangers may simplify the analysis (because participants cannot implicitly rely on shared knowledge), 'pre-acquainted' groups are sometimes more appropriate. For example, participants who are acquainted may find it easier to talk about their lives, or feel more comfortable about signalling a gap between what another participant says and what he/she does [START_REF] Kitzinger | The methodology of Focus Groups: The importance of interaction between research participants[END_REF]. They may find it easier to engage in a discussion about private issues if they feel more confident [START_REF] Hyde | The focus group method: Insights from focus group interviews on sexual health with adolescents[END_REF][START_REF] Hopkins | Thinking Critically and Creatively about Focus Groups[END_REF]. Yet in groups of strangers, participants can also develop trust and feel close to each other based on shared or similar experiences [START_REF] Albrecht | Understanding communication processes in focus groups[END_REF]. Thus, the composition of the focus group should be the result of a fine-grained negotiation between the research question, aspects for creating successful group dynamics and practical issues.

Physical organization and recording the data

In absolute terms, there is no such thing as a 'neutral' location. Choosing the site for the focus group should involve a balance between its accessibility and its potential effects on the discussion and thus on the co-constructed data (e.g. convening focus groups of couples receiving gamete donations in the fertility clinic where they go for treatments may be convenient, but might inhibit views that diverge from the clinic's principles: for example, donor anonymity, etc.). Sometimes it may be strategically desirable to conduct groups in a variety of different places in order to capture more or less normative answers [START_REF] Green | The Impact of Context on Data[END_REF].

In all cases, the venue should be free of external interruptions, and should allow a comfortable interpersonal distance between participants. This distance can vary depending on the cultural context and on the nature of the existing relationships. Seating the group in a circle, or at least in a way in which all members can easily see one another, facilitates engagement and discussion and reduces the tendency for particular participants to dominate or for subgroups to develop.

The decision to use audio or video recording should be guided by the study objective and the data analyses: Is it important to know exactly who is talking? Is an analysis of non-verbal data planned? Or will a thematic analysis be sufficient? The choice of video recording should be made primarily in cases where the first two purposes are central, as it is not always well accepted by participants, enhancing their self-consciousness and discomfort. Keep in mind that even the best recording and transcription can never completely faithfully reproduce a session, as some parts are often inaudible when the discussion is lively [START_REF] Kidd | Getting the Focus and the Group: Enhancing Analytical Rigor in Focus Group Research[END_REF]. The recording equipment should be of sufficient quality and quantity so that the moderator does not have concerns about the forthcoming transcription task and can concentrate on the group.

In the last decade, online focus groups have emerged as an alternative for participants experienced with electronic environments. Indeed, synchronous online focus groups approximate face-to-face discussion: the same interpersonal processes and are observed. Additionally, participants may be more inclined to engage in talking about sensitive topics as the discussion may be perceived as more informal [START_REF] Stewart | Online Focus Groups[END_REF]. Online focus groups also offer a unique possibility to bring together geographically dispersed participants, people in remote areas or those with disabilities [START_REF] Morrison | Extending the online focus group method using web-based conferencing to explore older adults online learning[END_REF]. As such, they can be considered as an expansion of research tools that offer novel and creative ways to conduct focus groups made possible by new technology [START_REF] Stewart | Online Focus Groups[END_REF]. However, as these communication technologies as well as people's experience using them are rapidly changing, it is difficult to draw firm conclusions regarding these alternative organization tools [START_REF] Lobe | Best Practices for Synchronous Online Focus Groups[END_REF].

Moderating the discussion

The moderator is fundamental to assure the flow of interactions, but his/her interventions should be far fewer than in individual interviewing. In order to allow group interactions to occur, the position of the moderator should be more like "the theatre manager rather than the director of the play" (Bloor et al., 2001, p. 49). Asking an unplanned question can run the risk of the group ceasing to interact with each other and addressing their answers to the moderator. Thus, a key rule of thumb is the less intervention, the better. However, this does not mean that the moderator should be passive; newcomers to focus groups are often surprised by how much energy is needed to moderate a discussion despite making few interventions. An effective moderator promotes discussion by his/her presence and attentiveness. Additionally, the moderator must manage the time, maintain the focus of the discussion, and prompt the next question. He/she must also pay particular attention to what is taken for granted by the group and ask participants for clarification in order to facilitate the future analysis (the best approach is to note questions and then ask them when the discussion stops naturally). Note-taking also has a function during the discussion: it makes explicit that the moderator is not in the foreground and that participants' answers are noteworthy. So although moderation may seem to be an apparently easy task, it should be carefully planned in advance when designing the study.

A first aspect to consider is what the moderator may represent for participants. In some cases, it may be advisable to have a moderator with the same cultural background as participants [START_REF] Smithson | Using and analysing focus groups: Limitations and possibilities[END_REF], or to have a woman conduct discussions with women in order to liberate discourse. In cross-cultural contexts, who moderates the discussion is also an important issue: a native-language but untrained moderator may jeopardize the quality of data, however, a trained moderator who does not speak the language of the participants would require an interpreter, and translations may slow down group interactions (see [START_REF] Hennink | Cross-cultural focus group discussions[END_REF]. Moreover, potentially difficult situations must be imagined and the best strategy to cope with them must be decided beforehand, always keeping in mind that social interactions have to be sustained. For example, rather than seeking equal participation, the moderator might invite participants who seem to have a minority point of view to express their opinion in order to further the discussion [START_REF] Smithson | Using and analysing focus groups: Limitations and possibilities[END_REF]. However, it is counterproductive to systematically ask all participants to express their view, as this may negatively impact the spontaneity of interactions. Participants who talk too much are frequent in focus groups, and it is helpful to plan how to manage this in advance: e.g. avoiding eye-contact with the dominant person, changing the subject immediately after the dominant person stops talking, and, in extreme cases, cutting him/her off by asking the rest of the participants another question [START_REF] Stewart | Focus Groups. Theory and Practice[END_REF]. In the goal of sustaining interactions, an alternative to cutting off acrimonious conflicts may be to regulate them by inviting the participants to theorize about their divergence of views. Additionally, it should not be forgotten that participants also have group management skills, and they may use these to regulate conflicts or to invite other more reticent participants to further explain their point of view [START_REF] Barbour | Doing Focus Groups[END_REF].

Selecting what to ask and how to ask it

It is important to create a guide that sets out the agenda of the discussion during the sessions; this is a crucial tool to ensure the relevance of the elicited data for the purpose of the study. The first step in developing this guide is the clarification and articulation of the detailed research questions, which are then turned into the questions to ask the participants. The guide will also anticipate the structure of (and to some extent the categories used in) the analyses. Yet while the guide will serve to structure and focus the discussions, as a qualitative tool it should be open enough to let unexpected answers arise [START_REF] Lunt | Rethinking the Focus Group in Media and Communications Research[END_REF]. Indeed, "focus groups are designed to determine how respondents structure the world, not how participants respond to the researcher's view of how the world or a particular phenomenon is structured" (Stewart et al., 2007, p. 72).

The structure outlined by the guide could take different approaches: e.g. different topics could be successively introduced to the participants in order to map their perspectives on different facets of the phenomenon under study. Or a funnel approach could be adopted (from general to more specific questions), allowing the researcher to first explore the salience of a specific topic for the group: does it spontaneously come up? If so, in what context? This can be useful in situating its place in the larger perspective of the general topic.

As the raw material for the analysis arises from interactions, the structure of the focus group must elicit and sustain these. When developing the guide, it is worth noting that giving the group tasks to perform can help maximize group cohesion, which in turn improves interaction [START_REF] Stewart | Focus Groups. Theory and Practice[END_REF]. Thus, the design could include ways to engage participants

Ethics

Ethical considerations should be ongoing and not end with the approval of the ethical committee. Beyond the focus group sessions, these considerations should encompass the whole research design. [START_REF] Barbour | Doing Focus Groups[END_REF] highlighted the potential consequences of a sampling strategy that brings together individuals with different experiences (e.g. newly diagnosed patients and those with advanced disease). If the design concerns a pre-existing group, the future impacts on the functioning of the group taking part in the research should also be taken into account: the potential for over-disclosure that might impair an individual's reputation, or damage to team relationships, etc.

An important ground rule is that in a situation where harmful misinformation has been shared in a discussion, the debriefing should include accurate information [START_REF] Hyde | The focus group method: Insights from focus group interviews on sexual health with adolescents[END_REF]. Depending on the topic, flyers with relevant information or contact numbers for helplines can be prepared. To the extent possible, difficulties arising during the group discussion should be anticipated by the moderator, who should also be prepared for the unexpected.

Conclusion

The brief historical overview of the methodology of focus groups outlines the multiple and diverse uses of the method, aiming to give some background to the very different rules of thumb that often create confusion for focus group novices. It situates the debates regarding focus group research in social sciences over the last decades in order to more clearly define focus groups as a methodology in which social interactions are used both as a way to elicit rich data and as data in itself. One of the key values of focus groups is that they highlight the collective processes of meaning construction. In this perspective, some useful innovations regarding both group composition and the materials used to stimulate discussion have been proposed in recent years to promote relevant group discussions. While we have focused on using the method as a research tool, the guidelines we have provided may also help in designing focus groups for other purposes (e.g. programme evaluation, promoting social change, etc.: see [START_REF] Linhorst | A Review of the Use and Potential of Focus Groups in Social Work Research[END_REF][START_REF] Liamputtong | Focus Group Methodology[END_REF]. These guidelines aim to offer some general principles, but do not touch on every type of innovation in the field or alternative strategies, such as the possibility of conducting dyadic interviews in a way similar to focus groups, or augmenting a group's heterogeneity [START_REF] Morgan | Conclusions: A call for further innovations in focus groups[END_REF]. Beyond this attempt to offer guidelines for using focus groups in a research context, we argue that their use in a broader research design furthers understanding of their specificities and allows opportunities for mixed-method or triangulation research design [START_REF] Caillaud | Focus groups in triangulation contexts[END_REF].

  Authors' version : Caillaud, S.,Kalampalikis, N. & Doumergue, M. (à paraitre). Designing Focus Groups. In U.Flick (Ed) The Sage Handbook of Qualitative Research Design. Sage and strategically used medical knowledge to block them, endorsing the traditional biomedical approach when evaluating the case: 1 Physician: In my opinion, she doesn't qualify for visual impairment assistance. Personally, [the psychological information] wouldn't change my point of view, but we could encourage her to seek help elsewhere.

	Teacher & Psychologist: Hmm.
	Physician: Well…it is a case of care, not impairment.
	…/…
	Researcher: So …
	Psychologist: Um yes, [in this case] we do not really know if there is visual
	impairment.
	School staff: But the physician has established that…
	Physician: It has been established, that's what we're telling you.

Authors' version : Caillaud, S., Kalampalikis, N. & Doumergue, M. (à paraitre). Designing Focus Groups. In U.Flick (Ed) The Sage Handbook of Qualitative Research Design. Sage

Authors' version : Caillaud, S., Kalampalikis, N. & Doumergue, M. (à paraitre). Designing Focus Groups. In U. Flick (Ed) The Sage Handbook of Qualitative Research Design. Sage in a mission that necessitates a spontaneous exchange of views and information that are relevant to the researcher [START_REF] Bloor | Focus Groups in Social Research[END_REF]. Confronting them with a dilemma on a theme relevant to the research aim is a good example. This provokes debate and conflicting views since no perfect solution exists.

Numerous innovative ways to facilitate focus group discussions have been developed [START_REF] Barbour | A New Era in Focus Group Research[END_REF], and there is still ample room for creativity. Focus group activities range from traditional spontaneous word association or ranking tasks through role playing (including dilemmatic vignettes, see [START_REF] Grossen | Processus d'influence, cadrage et mouvements discursifs dans un groupe focalisé[END_REF] to the physical engagement of participants in performance-based approaches (Wooten, 2017). Visual elicitation has also been successfully used: prompting participants pictures (images, photos, videos, comics, advertisements, etc., see e.g. DeVisser et al., 2005), or asking participants to express their opinions visually through drawings [START_REF] Devine-Wright | Social representations of electricity network technologies: Exploring processes of anchoring and objectification through the use of visual research methods[END_REF] or photovoice productions [START_REF] Sarrica | Photovoice as a visual-verbal strategy for studying contents and processes of social representations: a participatory project on sustainable energy[END_REF]. Other materials that can be used to stimulate discussion include newspaper articles, tests, questionnaire surveys, games, and even odours [START_REF] Cerisier | Reproduction sérielle d'un matériau odorant: de l'odeur sentie à la reconstruction collective de son souvenir[END_REF] or food [START_REF] Halkier | Practice theoretically inspired focus groups: socially recognizable performativity[END_REF]. Some authors [START_REF] Duarte | Site-specific focus groups: Analysing learning spaces in situ[END_REF] have recommended conducting focus groups in situ to capture how interactions develop in a spatial context. Essentially, any type of stimuli could become an effective prompt in a focus group, as long as it allows for counter-normative discourse and debate -however, not everything works for every topic and with any group! For example, in a Master's research project, one of our students used a spontaneous word association task on menstruation as a first question. This prompted the women in the focus group to talk for 45 minutes in a way relevant to the research aim before the second question was asked. In contrast, in another research project, a similar word association task on student jobs did not elicit valuable discourse as participants were not engaged with the topic. In some cases, even the absence of debate may constitute a relevant result: in one study, the differing amount and intensity of debate initiated by a similar dilemma in two different cultural contexts was considered in itself a valuable finding on cultural assumptions [START_REF] Marková | Dialogue in focus groups. Exploring socially shared knowledge[END_REF]. As a result, there is no such thing as a 'good' focus group task in absolute terms; the ethical and scientific justification for its selection should be based on its adequacy as regards both the sensitivity of the topic for the particular participants and the research objective.

The guide should provide a detailed plan for the focus group, with special attention paid to the way the discussion will be introduced. The moderator needs to make the aim of the discussion explicit at the outset, and should clearly invite participants to talk to each other. Participants come to this kind of discussion with their own assumptions: they may expect to learn something, or want to share emotions in a therapeutic way [START_REF] Breen | A Practical Guide to Focus-Group Research[END_REF]. Thus, the introduction must explicitly frame the discussion in order to avoid potential misunderstandings. For example, in a study on gamete donation, the first participant to start off the introductions began to tell other participants (all parents by sperm donation) the medical details about his infertility. The moderator then had the challenge of thanking him for his poignant experience-sharing, while implying that not all participants have to do so. In response, for the next discussion, the moderator suggested participants introduce themselves by giving their first name and the age of their oldest donor-conceived offspring in order to better frame the self-presentations. The discourse for the recruitment of participants should also be prepared carefully as it frames participants' expectations regarding the discussion. Once the first draft of the guide has been prepared, it should be tested with a pilot group. When considering the data arising from this pilot, two main questions can help in selecting the final stimuli materials and the questions to be asked: Did these elicit discussion effectively? Are the responses useful for the research question? The final guide can then be revised to address any issues before other focus groups take place. While it outlines the agenda for the focus group, the guide is often not long -in fact its brevity may be disconcerting given the amount of work involved in its development [START_REF] Barbour | Doing Focus Groups[END_REF].

Analysing the data

Transcription of the discussions is an important step in focus group analysis. Transforming a rich group discussion into a readable text that rigorously and vividly recounts what happened is a time-consuming and skill-demanding activity. Decisions have to be made regarding what is transcribed and what is not: for example, non-verbal cues [START_REF] Barbour | Doing Focus Groups[END_REF]. A common compromise is to follow the spirit of conversational analysis conventions without implementing them to the letter: all recorded speech (including interruptions, hesitations, pauses, etc.) should be transcribed without being edited, and the speakers should be identified [START_REF] Bloor | Focus Groups in Social Research[END_REF]. However, before the task, the transcriber should be aware of what will be analysed and thus needs to appear in the transcript.

For a long time, less attention was paid to the analysis of focus groups than to questions regarding their organization [START_REF] Wilkinson | Focus groups in health research: Exploring the meanings of health and illness[END_REF][START_REF] Kidd | Getting the Focus and the Group: Enhancing Analytical Rigor in Focus Group Research[END_REF]. Yet the essential and complex question of analysis should be considered in the very design of focus groups. A classical content or thematic analysis is not sufficient as it does not consider the role of social interaction in producing data; on the other hand, while a conversation or discourse analysis focuses on 'how' interactions occur, the topic/content is often neglected [START_REF] Morgan | Reconsidering the Role of Interaction in Analyzing and Reporting Focus Groups[END_REF]. Recently, studies have provided valuable and thought-provoking avenues to link focus group content and interactions. A theoretical starting point for the analysis could be to consider focus groups as social enactments in which data can be used to investigate certain patterns of everyday activities across contexts, as well as to show how these patterns become situationally negotiated [START_REF] Halkier | Focus groups as social enactments: Integrating interaction and content in the analysis of focus group data[END_REF][START_REF] Halkier | Practice theoretically inspired focus groups: socially recognizable performativity[END_REF]. [START_REF] Marková | Dialogue in focus groups. Exploring socially shared knowledge[END_REF] put forward a compelling starting point in presenting the main assumptions on which analytical tools should be based when focus groups are used to analyse the construction of socially shared meaning. They suggest a focus on (1) how the context, both as an external framework and as created and transformed by the group, shapes the communicative activity and meaning; (2) how participants communicate from different positions and identities; (3) how participants interpret each other's discourse and link their discourse with the discourse of others to produce meaning; and (4) how they rely on historically and culturally shared meanings. Alongside these more theoretical reflections guiding the choice of analytical tools, some more concrete propositions have also emerged regarding focus group analysis [START_REF] Smithson | Using and analysing focus groups: Limitations and possibilities[END_REF][START_REF] Lehoux | Focus group research and "the patient's view[END_REF]Andreouli et al., 2015;[START_REF] Caillaud | How groups cope with collective responsibility for ecological problems: symbolic coping and collective emotions[END_REF][START_REF] Morgan | A System for Coding the Interaction in Focus Groups and Dyadic Interviews[END_REF]. Another challenge for the researcher is how to present the results of focus group data in terms of reporting interactions [START_REF] Morgan | Reconsidering the Role of Interaction in Analyzing and Reporting Focus Groups[END_REF]. Whatever the case, to be consistent with the research aims [START_REF] Duggleby | What About Focus Group Interaction Data?[END_REF], the time-consuming process of focus group analysis may require developing a range of specific skills, picking from different methods of qualitative analysis in order to articulate what has been said (the content) and how it was said (the group dynamics).