Political Science 30
Political Inquiry
1. Homework #1 due today, start of
lecture.
2. Sections meet in Solis 105 this
week.
Measurement I. Knowing a Good
Measure When You See It.

Conceptual and operational definitions of
a variable

Examples:
Support for democracy
 Voter turnout in the U.S.


Measurement error and validity
Conceptual Definitions

A conceptual definition of a variable states
precisely what you mean when you use a
particular term.

A society that “supports democracy” is one
that emphasizes tolerance, trust, political
activism, and Post-Materialist values, not just
one that pays lip service to the ideals of
democracy. -- Ronald Inglehart
Conceptual Definitions

A good conceptual definition:
Looks at how other scholars have defined a
term, and goes with the consensus unless
there is a good reason to deviate.
 Allows you to test the theory that you want
to test.
 Is not circular (for example, does not say
that support for democracy is when the
public voices support for democratic values)

Operational Definitions

An operational definition of a variable is
a complete recipe for going out into the
world and measuring a variable.
It helps us make the leap from our
subjective impressions to an objective
measure.
 Like a recipe in any good cook book, a good
operational definition can be followed by
any other chef.

Operational Definitions

To measure “support for democracy,”
Inglehart uses the World Values/
European Values Survey from 1995-97
and 1999-2001 and looks at average
levels of agreement with nine statements
such as:

“Is it good to have a strong leader who does
not have to bother with parliament and
elections?”
Voter Turnout in the U.S.:
The Traditional Measure

Conceptual: “Turnout” is the percentage of
those who can vote who actually do.

The traditional operational definition is:
TotalVotesCast
Turnout 
VotingAgePopulation
Where Voting Age Population (VAP) includes
noncitizens and convicted felons, but not citizens
living overseas.
Voter Turnout in the U.S.:
The Traditional Measure
Voter Turnout in Presidential Elections
(% of Voting Age Population)
70
60
Turnout Rate
50
40
30
20
10
0
Year
Voter Turnout in the U.S.:
The McDonald & Popkin Measure

Conceptual: “Turnout” is the percentage of
those who can vote who actually do.
TotalVotesCast
Turnout 
VotingElig iblePopula tion
Where Voting Eligible Population is purged of
noncitizens and convicted felons but includes
citizens living overseas.
Voter Turnout in the U.S.:
The McDonald & Popkin Measure
70
Voting Age
Population Turnout
%
60
50
Voting Eligible
Population Turnout
%
40
30
20
10
0
1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004 2008
Measurement Validity
 Measurement
Validity gauges the
strength of your empirical measures.
It is highest when the gap between
your conceptual definition and your
operational definition is smallest.
Measurement Error
Measured Value =
True Value + Bias + Random Error
Sources of Measurement Bias:
1. Faulty instruments: scale is always off,
question wording always bad.
2. “Hawthorne Effect:” Humans behave
differently when they are being tested