What type of research involves in-depth study of a culture-sharing group?

The appropriate choice for an in-depth study of a culture-sharing group is ethnography. Ethnography is a qualitative research method primarily used in the fields of anthropology and sociology, where researchers immerse themselves in the daily lives and cultures of the participants. This approach is characterized by the collection of detailed observations, interviews, and the contextual background of the group being studied.

Ethnography emphasizes understanding the beliefs, values, and practices of a particular group from their perspective, which often involves long-term engagement with the community. This method not only captures the nuances of cultural practices and social interactions but also provides insight into how individuals within the group make sense of their experiences.

In contrast, grounded theory is aimed at generating a theory from data systematically collected and analyzed, rather than focusing solely on cultural observation. Quantitative designs typically involve numerical data and statistical analysis, which would not capture the deep cultural insights that ethnography provides. Mixed methods combine qualitative and quantitative approaches but do not exclusively focus on culture-sharing groups in the way that ethnography does. Thus, the richness and depth of understanding achieved through ethnography makes it the correct answer for this question.