Qualitative vs quantitative
Distinction is based on philosophical grounds - quantitative methods are associated with empirical, positivist research - often said to be inappropriate in relation to social research; qualitative research is associated with ‘anti-positive’ philosophies, such as interpretivism, ethnography, phenomenology, etc.
Notes:
With the different philosophical foundations comes the division of social research methods into two groups - quantitative methods, associated with positivism; and qualitative methods, associated with the anti-positivist schools of thought, especially, as noted earlier - hermeneutics and phenomenology, and widely employed in social research in recent years.