Introduction
Immigrants and their descendants are often considered a hard-to-reach population in survey research (Tourangeau 2014), and their integration into general population surveys remains an ongoing societal challenge in many countries. In Germany, for example, currently, about 30 % of the population has a migration background (Statistisches Bundesamt 2024), and this share is expected to rise. For the social and behavioral sciences, this demographic development underscores the urgent need to adequately include immigrant minorities in population surveys and panel studies. However, research consistently shows that respondents with a migration background exhibit higher rates of unit nonresponse (Jacobsen and Siegert 2023), making their inclusion both challenging and costly (e.g., Kühne et al. 2019). Innovative methodological approaches are therefore needed to improve participation among migrant populations.
Preliminary evidence suggests that participation among migrant groups can be improved through targeted communication strategies (Lynn 2017; Sladka and Lynn 2025) that go beyond questionnaire translation and address all stages of contact (De Leeuw et al. 2007). Research highlights the importance of culturally sensitive communication (Schenk and Neuhauser 2005; Stadler 2009). This includes adapting information materials, interviewer assignments, and communication styles to foster trust and respect (Mohammadi et al. 2008). Qualitative insights have occasionally been used to refine recruitment materials; however, experimental evaluations of their effectiveness remain scarce, highlighting a gap in survey research (Satia et al. 2005).
In addition, acknowledging linguistic and cultural diversity throughout the survey process is essential—by offering materials in respondents’ preferred language, employing culturally matched interviewers, and using familiar media channels for outreach (Zeisler et al. 2019). Moreover, collaborations with trusted community organizations can strengthen credibility and improve access to potential respondents (Bonevski et al. 2014). Together, these strategies can help to increase survey participation among migrant populations.
Although previous research has addressed survey participation among migrant populations, conclusive best-practice solutions remain elusive. This project addresses this methodological gap by pursuing two objectives: (1) developing culturally sensitive fieldwork materials in collaboration with members of the target population, and (2) systematically translating qualitative insights into experimentally varied fieldwork materials to make design decisions transparent.
The paper outlines how qualitative findings were translated into the design of tailored recruitment materials that are going to be tested in a survey experiment, resulting in an integrated mixed methods approach. Mixed methods research combines the strengths of two complementary perspectives—qualitative and quantitative—to generate insights that neither approach could achieve alone (Baur et al. 2017; DeCuir–Gunby 2008; Johnson et al. 2007). The paper presents and reflects on experiences from the completed qualitative phase and concludes by discussing the methodological implications for inclusive survey research.
Background: The “TaRec” research project to improve survey participation of Turkish migrants in Germany
Our research project aims to develop and test a tailored motivation and communication strategy for people with Turkish citizenship in Germany to foster both initial and continued participation for a multi-thematic panel study. With approximately 3 million individuals, they represent the largest migrant-origin group in the country (Statistisches Bundesamt 2024). Turkish-origin individuals consistently show lower response rates than other migrant populations (Brand et al. 2019; Reiss et al. 2014; Saß et al. 2015) and are less likely to participate in longitudinal surveys (Ruland and Sandbrink 2022).
The project follows a sequential mixed-methods design (Morgan 2014), combining qualitative exploration with quantitative field experiments. Insights from the qualitative phase informed the development of tailored recruitment materials, which are being evaluated experimentally in a quantitative phase regarding the initial contact with survey participants and gaining panel consent for a second wave in a panel study.
This paper describes how qualitative methods were used to inform the development of our fieldwork materials. Drawing on qualitative interviews, we show how the invitation letter and accompanying information leaflet were reframed, comparing a standard and a tailored version to be implemented across three modes: in-person, PAPI (i.e., paper questionnaires mailed to and completed by respondents), and CAWI (i.e., web surveys). We also discuss how the wording of the panel consent question was revised.
Designing a tailored, target group-specific recruitment strategy using qualitative insights
To inform our fieldwork strategies and the design of the advance letter and panel consent question, we combined three different qualitative methods: expert interviews with community leaders, as well as focus groups and cognitive interviews with persons of Turkish family background. Following recent research (e.g., Zeisler et al. 2019), this phase focused on developing target-group-specific fieldwork materials and recruitment strategies in collaboration with members and representatives of Turkish communities in Germany. In our methodological set up, we used the insights from expert interviews and a first round of focus groups to initially develop invitation and information materials. A second round of focus groups together with cognitive interviews were used to further refine those fieldwork materials. In particular, we developed a target-group specific cover letter, an FAQ leaflet, and a tailored panel consent request that aim to (a) raise interest and (b) establish trust among persons of Turkish background. The consent wording and framing were adapted while fully complying with GDPR requirements.
Methodological approach and sampling
Regarding expert interviews, we conducted 16 semi-structured expert interviews with stakeholders of diverse local community groups (n = 16, about 45 minutes each) between September 2024 and May 2025. The experts were selected using purposive sampling to ensure diversity across local contexts and organizational types. Interviews were conducted in Berlin, Cologne and other urban cities, covering areas with sizable Turkish-origin populations. The expert sample included representatives of mosques as well as secular associations, an Alevi community, a women’s association, migrant self-organizations, family associations and individuals working in community-related media or politics.
The interviews focused on strategies to build trust and develop culturally sensitive recruitment strategies. We inquired about how the group of Turkish migrants might perceive the request for survey participation and what kind of topics might be particularly important for them. We also asked for potential cultural barriers that researchers must be aware of when conducting the survey. Establishing ties with the experts also helped us recruit respondents for the focus groups.
Second, we worked with persons of Turkish family background in six focus groups to develop and refine target-group-specific materials between June and October 2025 (in total, n = 32 participants). The focus groups covered different genders, age groups, social backgrounds and duration of living in Germany. We recruited participants through personal contacts and contacts with community experts, as well as online groups on social media sites (cf., Weiner et al. 2017). The focus groups were conducted in the participants’ preferred language — German or Turkish — to ensure that they could express their views comfortably and accurately. The interview guide entailed specific questions on appeal of the materials, privacy concerns, incentives, recruitment materials, and trust-building strategies. Insights from this first round of focus groups informed the development of draft fieldwork materials and contact procedures. In the second round of focus groups, we then discussed the developed materials with participants to identify possible problems and solutions for finalising the fieldwork materials.
Third, we conducted cognitive interviews (cf., Beatty and Willis 2007; n = 8) to finetune the resulting fieldwork materials, the cover letters, and the request for panel consent and identify any remaining target group-specific issues. Interviews were conducted between June and October 2025. We recruited participants through personal contacts as well as via online groups on social media platforms. Some of them had previously taken part in the focus groups. We considered the overlap with focus group participants in the cognitive interviews acceptable because the participants had expressed interest in continued involvement in the project. Moreover, including them allowed us to verify whether their feedback from the focus groups had been accurately implemented in the draft fieldwork materials. Most participants identified either as “New Wave” Turks or as third-generation individuals of Turkish origin who were born and raised in Germany. Compared to the focus group participants, they tended to be younger, being in their mid-20s to mid-30s which was a good addition to the diversity of the sample.
Results
Insights from the qualitative research methods
From the qualitative interviews, we identified four main findings:
First, participation emerged as an issue of trust. In the expert interviews, participants described that previous negative experiences that Turkish-origin individuals make in their everyday life led to a broader, structural mistrust toward the state, public institutions, and data protection. Importantly, “the state” was often not understood as a clearly defined set of actors, but rather as a vague and undifferentiated notion encompassing various authorities and official bodies. In participants’ accounts, this was closely linked to practical uncertainties during first contact, such as not knowing who exactly sent a survey invitation and concerns about potential fraud. At the same time, some experts noted that levels of trust may vary, with German public institutions in some cases even being perceived as more trustworthy than Turkish ones. In the focus groups and cognitive interviews, similar experiences were shared and discussed across almost all age groups. This suggests that mistrust is not limited to specific subgroups but is a widespread factor influencing decisions about whether to take part in research.
Second, questions of belonging emerged as a key factor influencing participation. Across almost all interviews and focus groups, a recurring sentiment was, “This is not for people like me.” When individuals do not feel connected to mainstream society, surveys that address the general population often fail to make them feel included. These reactions were closely tied to experiences of exclusion and the sense of still being seen as “guests” or “foreigners.” The focus groups, in particular, provided an open space for participants to talk about these emotional experiences in detail.
Third, language was generally not seen as the main barrier to understanding the materials. Rather, it was described as a tool to convey respect and recognition. In focus groups and cognitive interviews, participants mainly were able to understand the content in German, but bilingual materials and also translation quality mattered for how professional and engaging the materials felt (as discussed further below in the section on findings from the cognitive interviews). Thoughtful use of language strengthened trust and made the participants feel appreciated, which in turn increased willingness to participate.
Fourth, age, education, language skills, and length of residence were not seen as primary barriers to participation. Instead, they highlighted existing mistrust and feelings of exclusion. In other words, sociodemographic characteristics shaped how strongly individuals experienced hesitation or scepticism toward surveys, but they rarely seem to affect low participation on their own.
Translation of qualitative insights into survey materials
Based on the qualitative findings, we developed tailored fieldwork materials, detailed below.
Initial Contact
The tailored version of the invitation letter was informed by qualitative findings indicating several reasons for higher nonresponse rates among Turkish-origin individuals, including mistrust, feelings of lack of belonging and language barriers. We translated these insights into specific design elements in the invitation letter (Table 1).
The Appendix contains the German and Turkish versions of the tailored and untailored invitation letters, information brochures, and panel consent questions used in the study, as well as an english translation. Tailored passages are highlighted in yellow. The examples shown are based on the PAPI mode.
In the invitation letter, we addressed the mechanism of mistrust through an appreciative and respectful introduction acknowledging Turkish communities and their contribution to German society. Experiences of social exclusion were explicitly referenced to signal recognition of lived realities. We also included a well-known Turkish proverb to appreciate the recipients’ language and culture. Furthermore, we highlighted underrepresentation in surveys to frame participation as socially meaningful, and the availability of a Turkish-origin contact person was emphasized to reduce potential mistrust and enhance accessibility.
In the tailored version of the FAQ leaflet, we highlighted the topic of discrimination by mentioning it in the beginning of some of the topics that are covered in the questionnaire. We also addressed the recipients as persons of Turkish family background and emphasized their underrepresentation in research in this context as well.
The cognitive interviews led to several final adjustments. For example, the phrase “Ihre Ansichten können nicht mit anderen ausgetauscht werden” (literally: “Your views cannot be exchanged with others”) was perceived as ambiguous in the Turkish language. Participants in cognitive interviews suggested clearer and more appreciative formulations that are more commonly used and familiar in Turkish. Furthermore, another feedback from the cognitive interviews was that the introduction of the project team came too late in the letter. Therefore, we moved the information about who the research team is into the first two paragraphs to foster trust early on. These adjustments ensured that the materials were both comprehensible and perceived as appropriate by members of the target group.
Panel Consent question
In the tailored version of the panel consent question, the target group is addressed explicitly: instead of referring broadly to “people in Germany” the invitation specifies that the study is interested in how “people with family roots in Turkey experience their everyday lives in Germany.” This formulation makes the invitation identity-specific and directly acknowledges recipients’ ancestry. Additionally, the description of the study’s societal relevance is reframed. Rather than referring generally to “existing challenges,” the tailored version explicitly mentions “exclusion and lack of recognition” as potential consequences affecting social cohesion. In doing so, the invitation connects participation to making visible the consequences of discrimination and to identifying ways to improve social cohesion.
Discussion
The qualitative phase of our mixed-method study on panel recruitment for Turkish migrants in Germany allowed us to uncover cultural, linguistic, and motivational factors that standard survey procedures may overlook. We used the qualitative findings directly to design survey materials that are going to be tested in the quantitative phase of the project. For example, we varied wording, tone, and language choices in the cover letters and consent forms and discussed their potential impact on participation with members of the target population. Based on the qualitative interviews, we also gained insights into the community’s perceptions of social science research, trust in institutions, and preferences for communication and incentives. For example, participants repeatedly expressed that standard survey invitations felt impersonal or “not for people like me,” highlighting how lack of belonging and exclusion shaped their willingness to participate. Without such rich qualitative insights, these experimental conditions would have lacked grounding in participants’ lived experiences.
Our own experiences during the qualitative phase have underscored how essential such in-depth, dialogical spaces are for understanding participation barriers. When approaching participants for the qualitative phase, we found that trust could not be built through formal communication alone. Personal engagement, transparent discussion of research aims, and the ability to speak the participants’ language were central to establishing rapport. The focus groups, in particular, have been an appropriate and sensitive setting to discuss the recruitment materials in detail. These conversations went far beyond design preferences: participants connected their reactions to broader experiences of discrimination, and a perceived lack of belonging in German society. Such discussions are crucial for understanding how trust, identity, and everyday experiences shape willingness to participate in research. Thus, the qualitative phase not only informed recruitment strategies but also created opportunities for participants to voice perspectives and emotions that are rarely captured in standardized survey instruments.
Another important aspect was to test the usage of identity-specific wording that was suggested by the experts. Addressing participants as “people with a Turkish family background” can be empowering. However, there is a risk of essentializing participants or reducing them to their background. This made it crucial to test the wording carefully. Engaging participants from different generations and age groups helped us to ensure that the tailored materials sound inclusive and culturally sensitive.
However, the approach also has limitations. Mixed methods designs are resource-intensive, requiring careful planning, coordination, and sufficient sample sizes to ensure meaningful experimental results. In our study, the qualitative phase alone encompassed several months of data collection, processing, and analysis by multiple researchers, as the expert interviews, focus groups, and cognitive interviews were conducted consecutively. It also involved separate ethical approval procedures for the qualitative and quantitative components; substantial time and effort to transcribe and translate audio recordings from interviews and focus groups, even though computer-assisted tools were used; financial resources for fieldwork and participant incentives and software for qualitative data analysis. Gaining access to the field for the qualitative component was particularly time-consuming, as it required repeated personal contact and continuous communication to identify and motivate members of the target population for participation in the interviews. Moreover, while the qualitative findings inform tailored interventions, focus group and interview participants may not fully represent the diversity of the target population, potentially limiting the generalizability of the qualitative insights.
By integrating qualitative and quantitative methods, the project aims to both understand the underlying causes of low response and consent rates and experimentally test strategies to improve participation under real-world conditions. As a next step, the tailored recruitment materials developed during the qualitative phase, including both the invitation materials and the panel consent question, are being evaluated in a quantitative recruitment experiment across three survey modes: in-person, PAPI, and CAWI. The experiment will assess whether culturally and linguistically tailored recruitment strategies improve survey participation among Turkish migrants in Germany. The primary outcomes will be initial participation and consent to future waves. If the tailored materials increase participation and consent rates, the findings will provide evidence on the effectiveness of targeted fieldwork materials across modes and contribute to the development of more inclusive recruitment strategies for panel studies.
Funding information
This work and the underlying study are funded by the German Research Foundation (DFG) as part of the Infrastructure Priority Programme 2431, “New Data Spaces for the Social Sciences” (Grant No. 539582703).
Corresponding author contact information
Michael Weinhardt, michael.weinhardt@dza.de; Deutsches Zentrum für Altersfragen, Manfred-von-Richthofen-Str. 2, 12101 Berlin, Germany.