Definition Qualitative data

Qualitative data refers to an attribute whose values (such as survey responses) falls into clear categories. Typical examples of qualitative data include gender, religion, and political affiliation. For these kinds of attributes, we can only reproduce percentage values as results of a survey (x in 100%).

Strictly speaking, ordinal data such as education level and personal satisfaction level can also be classified as qualitative data. Although is is possible to establish a hierarchy of ordinal data, it is not possible to establish a precise numerical scaling. One level of education is not "50% better" than another but can be specified as "more than / less than" another level of education.

Sometimes, ordinal features are described as 'seemingly quantitative', because they allow for some mathematical comparisons. For instance, it is possible to can state that group A 'on average' has a higher level of education than group B. In order to achieve this, the ordinal levels of education are translated into numerical values (1=lowest education level, 5=highest education level). From these numerical values, we can calculate a mean for each group and then compare both values.