Nominal – numbers are either the same or not
Ordinal – if different, one number is bigger than the other
Interval – differences in numbers can be compared
Ratio – zero is a significant point
The properties described are nested – nominality is needed for ordinality, which in turn is needed for interval-ality, in turn needed for ratio-ality.
Anything interval level and above is considered quantitative. Most qualitative measures serve only nominal function, i.e. whether something is the same or not.
More formally: http://en.wikipedia.org/wiki/Level_of_measurement [HT: Soo Mei]
[...] Qualitative / Quantitative [...]