But there is also a strong ethical objection to case studies for that same reason: the lack of objectivity in accumulating facts may actually allow for greater bias on the part of the researcher. Since the researcher has a higher level of participation amongst his or her study subjects than an individual merely accumulating data, he or she might favor certain personal points-of-view, based upon favoritism of some community members. The intensely subjective nature of research might also yield more of a portrait of the researcher's perceptions, rather than of the population itself. Advocates of a more experimental approach to research would likely point out that case studies are not inherently 'better' than quantitative data in filtering bias. After all, Margaret Mead's famous anthropological study Coming of Age in Samoa has been widely critiqued because of the anthropologist's relatively filtered contact with the Samoan people. Furthermore,...

experimental study approach may be not to frame the supposed conflict as a debate at all, but to use both methods to paint a full portrait of human experience. After all, while statistical data is vital to track the effectiveness of a new retroviral drug for AIDS, a case study approach might be necessary to fully understand why some individuals are not compliant with treatment, and what cultural and social barriers might exist in enabling individuals to understand why taking the drug is so vital for their health.
Reference

DePoy, Elizabeth & Laura N. Gitlin. (2005) Research: Understanding and applying multiple strategies. Mosby.