Units of Analysis and data structure

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Units of Analysis and data structure

• The Basics

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Outline

• Definitions
• Elements of the unit of analysis
• Data structure

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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.

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Unit of analysis

• The unit of analysis is the object about which
  generalizations are made based on an analysis.

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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.

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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.

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Identifying units of analysis

• The unit of analysis is shaped by three
  properties
• Social entities
• Time
• Space

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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

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Social Phenomena

• transactional observations that are the result of
  actions among entities, such as labour strikes or
  international conflicts, including wars.

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Time

• observations made at one point in time a
  cross-sectional study

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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

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Space

• observations made within a specific spatial area
• observations made within a hierarchy of spatial
  areas

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Substituting units

• There may be requests for which data for a
  desired unit of analysis cant be delivered but
  for which data are available summarized over one
  of the other attributes of the unit of analysis.

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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

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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)

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Statistical data structure

• Lets review basic data structure.
• The unit of analysis defines the underlying
  structure of a data file.

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Statistical data structure

• 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.

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Statistical data structure
Case n-1
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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.

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Statistical data structure
Case n-1
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Statistical data structure
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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.

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Statistical data structure
Spreadsheet
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Statistical data structure
Spreadsheet
Cell B2
Cell E3
Cell C5
Cell F7
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Statistical data structure
Statistical Data Structure
Row 1
Row 3
Row k-1
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Statistical data structure

• The next slide presents the way that this simple
  statistical data structure appears in SPSS.

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Row 1
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Row 8
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Row 8
Row 15
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Field 8
Row 8
Row 15