Units of Analysis and data structure The Basics. Outline Definitions Elements of the unit of...
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Transcript of Units of Analysis and data structure The Basics. Outline Definitions Elements of the unit of...
Units of Analysis and data structure
The Basics
Outline
Definitions
Elements of the unit of analysis
Data structure
Unit of observation
The unit of observation is a basic concept in quantitative research that represents the objects that are observed and about which information is systematically collected.
Unit of analysis
The unit of analysis is the object about which generalizations are made based on an analysis.
Determination
The unit of observation is determined by the method by which observations have been selected;
The unit of analysis is determined by an interest in exploring or explaining a specific phenomenon.
When they are the same
The unit of observation and unit of analysis are the same when the generalizations being made from a statistical analysis are attributed to the unit of observation.
Identifying units of analysis
The unit of analysis is shaped by three properties:
Social entities
Time
Space
Social entities
observations of a single social entity, such as a person or an institution
observations of multiple entities with a defined relationship, such as family, employer-employee
Social Phenomena
transactional observations that are the result of actions among entities, such as labour strikes or international conflicts, including wars.
Time
observations made at one point in time: a cross-sectional study
Time
observations made at multiple points in time
the data may be organized by time; commonly referred to as a time series
time may structure some form of repeated measures of content or subjects
Space
observations made within a specific spatial area
observations made within a hierarchy of spatial areas
Substituting units
There may be requests for which data for a desired unit of analysis can’t be delivered but for which data are available summarized over one of the other attributes of the unit of analysis.
Substituting units
Example:
Request for firm-level data for NAICS 312 Beverage and Tobacco Product Manufacturing
Ideal source: microdata on establishments from the Canadian Census of Manufacturers
No access to enterprise microdata
Substituting units
Example: NAICS 312
Alternatives: are there aggregate data summarizing the firms within NAICS 312?
Possibilities: summaries over time (time series) or geography (small-area business statistics)
Statistical data structure
Let’s review basic data structure.The unit of analysis defines the underlying structure of a data file.
This structure consists of a series of rows with each row containing the data of one member of the unit of analysis.This simple structure is known as the flat, rectangular data matrix.
Statistical data structure
Case 1
Case 2
Case 3
*
Case n
*
*
Case n-1
Statistical data structure
Statistical data structure
All of the information collected for each member of the unit of analysis is organized in a fixed location in the file called fields or variables.
Case 1
Case 2
Case 3
*
Case n
*
*
Field 1*Field2
Field 3* Field k-1
Field k
Case n-1
Statistical data structure
Case 1
Case 2
Case 3
*
Case n
*
*
Field 1*Field2
Field 3* Field k-1
Field k
Case n-1
Statistical data structure
Statistical data structure
This structure looks like the grid of a spreadsheet. However, there is one very important difference between a statistical data structure and a spreadsheet.
The spread sheet is organized around individual cells, while the statistical data structure is organized around the rows.
Spreadsheet
Statistical data structure
Cell B2
Cell E3
Cell C5
Cell F7
Spreadsheet
Statistical data structure
Statistical Data Structure
Row 1
Row 3
Row k-1
Statistical data structure
Statistical data structure
The next slide presents the way that this simple statistical data structure appears in SPSS.
Row 1
Row 1
Row 8
Row 1
Row 8
Row 15
Row 1
Row 8
Row 15
Field 8