Quantitative and qualitative processes are named as such primarily due to the type of data they chiefly collect. In the quantitative research process, the researcher is paramountly concerned with the collection of information which is more objectively quantified. That is to say, quantitative data is data which can be measured using objective, uniform, and universal units. Those sciences known as ‘hard’ sciences are chiefly concerned with such measurements. Traits such as height, length, time, etc. - which can be measured using recognized units - are good examples of quantitative data. In contrast, qualitative data is that which is less easily - or at least less objectively - assigned a numerical value. Emotional responses, attitudes, and values, for example cannot be described using a numerical value system alone; any numerical value system utilized to describe or measure such things, must be carefully described by the user and applied in highly contextual circumstances. To a large extent the ‘soft’ sciences are so called because they are heavily dependent on this sort of data collection.
Creswell, J. W. (2002). Educational research: Planning, conducting, and evaluating quantitative (pp. 146-166). Upper Saddle River, NJ: Prentice Hall.