1. Populations and object types
European Statistical Training Programme 2008
Populations and object types
Contents
Introduction
Why do metadata anyway?
Populations
Object types
Variables
‘Systematic‘ way of defining populations
Relationship with data sets
Questions
Tjalling Gelsema (Statistics Netherlands)

2. Why do metadata anyway?
Organizing large amounts of statistical information
Informing interested people about how statistical information should be interpreted
Steering the (automated) statistical production process
Providing a structured, systematic way (language, pattern, frame of mind) for statisticians to record statistical information

3. What is a population?
“The total set of elements or the collection of all individuals, items, or objects under consideration in a statistical inquiry” (Wikipedia)
“Any finite or infinite collection of ‘units’, which are often people but may be, for example, institutions, events, etc.” (Cambridge Dictionary of Statistics)
Is a set
Its members can be observed and measured
It is clear for any object whether or not it is a member
Members occur only once
Is delimited by time and space
Subset: subpopulation

4. Examples
The set of all car accidents that occurred on April in Amsterdam
The set of all people in Delft on April
The set of all households
The Dutch agricultural sector in 2009
The set of all sectors of the Dutch economy on April
The set of natural numbers (on April )
Anyway, we need universes (of car accidents, people, households, etcetera)

5. Universe: object type
Set of objects that are suitable for observation.
Has a definition
Has variables (characteristics, properties)
Objects can be multiple time instances of same ‘item’
Each object can tell the time
Subset: object sub-type (super-type)
Object can be member of many object types

6. Object types and variables
In order to study object types, we need to study variables, and vice versa!
An object type can be defined through properties its objects have in common (= constant values according to variables of some super-type)
A variable is attributed to an object type
‘Systematic’ way of relating object types and defining populations. Building blocks: object types, associations, variables.

7. Object types

8. Object sub-types

9. Associations

10. Variables

11. Classification

12. Population types

13. Why do we need all this?

14. Questions ?