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.
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.
Statistical data structure
Case 1
Case 2
Case 3
*
*
*
Case n-1
Case n
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.
Statistical data structure
*
Case 1
Case 2
Case 3
*
*
*
Case n-1
Case n
*
Statistical data structure
*
Case 1
Case 2
Case 3
*
*
*
Case n-1
Case n
*
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.
Statistical data structure
Spreadsheet
Statistical data structure
Spreadsheet
Cell B2
Cell E3
Cell C5
Cell F7
Statistical data structure
Statistical Data Structure
Row 1
Row 3
Row k-1
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
Field 8
Row 1
Row 8
Row 15