The dictionary definition of "statistics" refers to numeric indicators of nations. Popular usage of the term points to numeric summaries that condense information, or numbers that are used to make comparisons, or numbers that portray relationships or associations.
The term statistics also refers a formal discipline of study. The field of statistics is the science of generalization. Built upon theories of probability and inference, statistics support the making of broad generalizations from a smaller number of specific observations.
The unit of observation is the same as the unit of analysis when the generalizations being made from a statistical analysis are attributed to the unit of observation (i.e., the objects about which data were collected and organized for statistical analysis).
While the units of observation and analysis are often the same, the wealth of secondary data sources creates opportunities to conduct analyses with data from multiple units of observation. This is probably most recognizable in GIS research.
Example: A major national study uses a form that collects information about each person in a dwelling and information about the housing structure. Therefore, this study collects data for two units of observation: persons and housing structures. From these data, different units of analysis may be constructed: Household could be examined as a unit of analysis by combining data from people living in the same dwelling. Family could be treated as the unit of analysis by combining data from all members in a dwelling sharing a familial relationship. This expresses how the unit of analysis can be constructed from units of observation consisting of some type of relationship constructed by time, space or social properties.
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