Numerical data

Numerical data usually comes in the form of tables of numbers, kind of like database tables. One of the most common data in this form is metrics data – for example, the standard object-oriented metrics that have been used since the 1980s.

Numerical data is often the result of a measurement process. The measurement process is a process where we quantify the empirical properties of an entity using measurement instruments to a number. The process must guarantee that important empirical properties are preserved in the mathematical domain – that is, in the numbers. Figure 6.1 shows an example of this process:

Figure 6.1 – The measurement process with an example of quality measurement using defects

The important part of this process consists of three elements. First is the measurement instrument, which needs to map the empirical properties to numbers in a true way. Then, there are the measurement standards, such as...