Assigning numbers to characteristics of objects according to specified rules in such a way that the numbers reflect the relationships that occur between these objects. The purpose of the measurement is to present the results of the statistical observations made on statistical units so that the symbols are related similarly as the interrelated units, events or phenomena describing these concepts.

The widespread use of numbers as these symbols is due to the fact that the relationships between numbers have been most thoroughly investigated by mathematics and the fact that some of the compounds are observed in the observations.

• Statistical series

• Statistical unit
• Statistical observation
• Ordered rank
• Measurement scale