Qualitative research is a methodology that can be applied to textual data. In Digital Humanities, the term would be "close reading" (as compared to "distant reading" like text mining).
"Qualitative data analysis is the classification and interpretation of linguistic (or visual) material to make statements about implicit and explicit dimensions and structures of meaning-making in the material and what is represented in it. Meaning-making can refer to subjective or social meanings. Qualitative data analysis also is applied to discover and describe issues in the field or structures and processes in routines and practices. Often, qualitative data analysis combines approaches of a rough analysis of the material (overviews, condensation, summaries) with approaches of a detailed analysis (elaboration of categories, hermeneutic interpretations or identified structures). The final aim is often to arrive at generalizable statements by comparing various materials or various texts or several cases."
Examples of Qualitative Research Methodologies:
Interview-based Data Collection
Archival and/or Historical Comparative Analysis
Social Media Analysis
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