Download - Measurement
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MeasurementAndrew Martin -- PS 372
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What is measurement?
• Measurement is the process by which phenomena are observed systematically and represented by scores and numerals.
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Operationalization
• Political scientists have figure out how to measure the presence of absence of concepts in the real world.
• The process requires political scientists to provide an operational definition of their concepts. Sometimes this is called operationalization.
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© Judith A. Perrolle 1987
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Operationalization Examples
• Concept: Fundraising
• Operational definition: Itemized receipts of daily campaign contributions made to each presidential candidate (FEC Database) (Haynes, Crespin, Zorn (2004) )
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Operationalization Examples
• Concept: legislator ideology
• Operational definition: Legislator ratings from Americans for Democratic Action, which is set on a 100-point scale, 0 being “most conservative” and 100 “most liberal.”
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What about corruption?• How would one operationalize corruption?
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Political Corruption• Most define political corruption as the use of
legislated powers by government officials for illegitimate private gain.
• However, if one were going to going to operationalize political corruption, how would it be measured?
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Transparency Int'l• Transparency International is a non-
governmental organization that tracks corruption in the public sector around the globe.
• The Corruption Perceptions Index (CPI) focuses on corruption in the public sector.
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Corruption Perceptions Index
• The surveys used in compiling the CPI ask questions relating to the abuse of public power for private benefit.
• These include questions on:
– bribery of public officials
– kickbacks in public procurement
– embezzlement of public funds
– strength and effectiveness of public sector anti-corruption efforts
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Corruption Perceptions Index
• Measures the perceived levels of public sector corruption in 180 countries and territories.
• A composite index based on 13 different expert and business surveys.
• Is not intended to measure a country's progress over time.
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U.S. Corruption?• U.S. DOJ Public Integrity section tracks data on
the number of federal, state and local government officials prosecuted and convicted for corruption crimes.
• The data the provide the number of people prosecuted by each U.S. Attorneys office.
• Corruption isn't clearly defined, but cases include election fraud, obstructing an investigation and violation of campaign finance regulations.
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Three-step process
• 1. Abstract concept
• 2. Conceptual definition
• 3. Operational definition
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Measurements
• The quality of measurements is judged with regard to both accuracy and precision.
• Accuracy refers to how close the measure comes to explaining the true value of a concept.
• Precision refers to the consistency of the measure in quantifying the concept.
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Measurements
• Reliability is the extent to which an experiment, test or any measurement procedure yields the same results in repeated trials.
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Testing MeasurementsTest-retest
method -- Apply the same test to the same observations after a period of time has passed.
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Testing Measures
Alternative-form method -- Use two different measures of the same concept rather than the same measure.
Ex: Using two different kinds of ideology measures for legislators.
NOMINATE scores vs. Interest Group scores
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Testing Measurements
• Split-halves method -- Using two different measures with both measures applied at the same time.
• Ex: Nominate and IG scores both in the same statistical model
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Measurements
• Validity -- the degree of correspondence between the measure and the concept it is thought to measure.
• Examples of validity issues -- Native Americans on U.S. Census, racial politics research, election turnout and voting
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Measurements
• Face validity is asserted by arguing that a measure corresponds closely to the concept it is designed to measure.
(Ex: Party ID and Ideology)
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Face ValidityTo confirm the validity of ideology and political party identification measures, I could examine their relationship:
Political Party U.S. Senate U.S. House
Republicans 20 16
Democrats 87 92
2007 ADA score based on a 100-point scale, with 0 meaning “always votes conservative” and 1 meaning “always votes liberal.” The measure is typically based on 20 voters in the 2008 congressional session.
Senators of interest:Obama: 75 (15 votes 15/15) McCain: 10 (15 votes 2/15)
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Measurements
• Content validity is demonstrated by ensuring that the full domain of a concept is measured.
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Content Validity
• Example: Dahl’s polyarchy
• Polyarchy, according to Dahl, is a form of representative democracy characterized by a particular set of political institutions. These include elected officials, free and fair elections, inclusive suffrage, the right to run for office, freedom of expression , alternative information and associational autonomy.
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Content Validity
Domain: Dahl book
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Measurements
• Construct validity is demonstrated for a measure by showing that it is related to the measure of another concept.
• Ex: Ideological identification and level of education.
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Inter-item Association
• Inter-item association relies on the similarity of outcomes of more than one measure of a concept to demonstrate the validity of the entire measurement scheme.
• Ex: Candidate strength can be cross validated by comparing measures of campaign funds, polling numbers, primary votes and newspaper coverage.
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Correlation• A correlation indicates the direction and
strength of a linear relationship between two random variables.
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