Combination Research is the best data collection method for a researcher that collects qualitative data, which is data based on respondents' feelings, opinions, and ideas.
Combination research is the best option because that combines the advantages of interviews and focus groups. It's also useful for gathering confidential data. It's a general-purpose quantitative data collection method.
Above all, whether compared to these other qualitative data collection methods, combination research improves the quality of data gathered.