Data are gathered facts, describing reality. Data are physically recorded observations of reality, facts, findings, skills or knowledge. Data exists and are stored in a variety of mediums or storage (paper, electronic data medium, mind). By data interpretation and their relationships with knowledge are formed information.
One of the basic structures divides the data to:
- Quantitative data - numerical characteristics of the given phenomenon (e.g. price, size, weight,…), sometimes the term “hard” data is used
- Qualitative data - non-numeric characteristics of the given phenomenon (e.g. customer satisfaction), sometimes the term “soft” data is used
In the concept of statistics, the data (or variables) are usually classified according to the type of relations between the values of:
- Nominal data - the nominal values of two variables can be said whether they are identical or different (e.g. manufacturer, model, type …)
- Ordinal data - as nominal values, in addition for the two extra ordinal variables, we can determine the order (e.g. the degree of customer satisfaction, product quality evaluation, …)
- Cardinal data - numeric variables, this group of variables is further divided into:
- Differential (Interval) - as ordinal, in addition you can determine how much more is one value than the other
- Ratio - as a differential, in addition you can calculate how many times is one value more than the other
Nominal and ordinal variables belong into the qualitative data. Differential and ratio variables belong into the quantitative data.