Participant observation is a hallmark of qualitative research. It involves the researcher immersing themselves in a social setting to gain an in-depth understanding of human behavior, social interactions, and cultural meanings from the perspective of the participants. This method prioritizes descriptive, narrative, and subjective data over numerical or statistical measurements.

Triangulation is a research technique that uses multiple data sources, methods, or investigators to study a single social phenomenon. By combining different approaches, researchers can cross-verify their findings, which enhances the validity and credibility of the study results by reducing the biases inherent in using only one method.

A research design serves as the blueprint for a study. It outlines the specific methods, procedures, and strategies a researcher will use to gather and analyze data, ensuring that the investigation is rigorous, replicable, and logically sound.

While ethnography is a vital qualitative method, it is often categorized as a specific type of field research rather than a distinct 'major research design' in some textbooks, which group it under the broader umbrella of field research. This classification can vary by academic source, but in this context, it is treated as a sub-method rather than a primary design category like surveys or secondary analysis.

A household account book is a private, personal document intended for the owner's use, making it inherently restricted. While medical records are confidential, they are professional documents managed by institutions. Government white papers and business registers are public or semi-public records. The household account book represents a primary source of personal data that is rarely accessible to external researchers without explicit consent.

Qualitative data consists of descriptive, non-numerical information such as interview transcripts or field notes. Because this data lacks a standardized numerical format, it is inherently difficult to organize into structured databases or tabulate into statistical tables, unlike quantitative data which is designed for mathematical analysis and measurement.

Ethnographic research relies on immersion and participant observation to understand social phenomena. Because it focuses on the meanings, experiences, and cultural nuances of participants from an 'insider' perspective (emic approach), it generates descriptive, non-numerical data that provides deep context rather than broad statistical generalizations.

Ethnographic research aims to reach an in-depth, meaningful understanding of a particular social group or setting. It typically involves the researcher immersing themselves ‘in the field’ that they are studying, by living with the group and observing their activities; they may also interview group members and collect documentary evidence. These kinds of data are qualitative: rich in detail and meaning.

Field research involves the direct collection of information from the natural environment where social phenomena occur. Because the researcher gathers this information firsthand through methods like observation or interviews, it is classified as primary data, which is original information collected specifically for the research project at hand.

The comparative approach in sociology involves examining data from different societies or nations to identify patterns, similarities, and differences. This method is essential for understanding how social phenomena, such as crime control, vary across diverse cultural and political contexts.