Transcript Conditions for Establishing Cause

Quantitative Research
Designs
V. Darleen Opfer
Conditions for Establishing CauseEffect Relationships:
Covariation
 Temporal Precedence
 No Plausible Alternative Explanations
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Types of Alternative Explanations
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History
Testing
Instrumentation
Regression
Mortality
Maturation
Selection
Selection by
maturation interaction
Ambiguity about
causal direction
 Diffusion of
treatments
 Compensatory
equalization of
treatments
 Compensatory rivalry
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Ways to Minimize Threats to
Validity:
By
 By
 By
 By
 By
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argument
measurement or observation
analysis
preventive action
design
Individual/Agential
Variables
Values
Psychological
Mechanisms
Political
Interest
Personal
Knowledge/
Experience
Newspaper
Coverage
Newspaper
Impacts
Norms of
Journalists
Structural/ Social
Variables
Newspaper
“Market Forces”
Class, education,
gender, ethnicity,
age, etc..
Causal relations
Intervening variables
Social
Networks
Trust in Media
& Government
(i.e., Public
Schools)
Basic Design Elements
Time
 Program(s) or Treatment (s) = X
 Observation(s) or Measure(s) = O
 Groups or Individuals =
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R = Randomly assigned groups
An Example:
R
O
R
O
X
O
O
Expanding a Design:
X
O
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Expanding across time
Expanding across programs
O O X O
O X O O X O
O X1 O
O X2 O
Expanding across observations
O1O2 X O1O2
 Expanding across groups
R O X O
R O
O
N O
O
______________________________
R O X O
R O
O
N O
O
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A Strategy for Design Construction
Depict the hypothesized causal relationship
 Identify the possible alternative explanation
threats
 Over-expand the basic design by expanding
across time, program observations, and groups
accounting for as many alternative explanations
as possible
 Scale back the design to a manageable plan by
considering the effect of eliminating each design
component
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The Nature of Good Design
Theory-Grounded
 Situational
 Feasible
 Redundant
 Efficient
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Design Task
A principal/head teacher wants to know whether the provision
of professional development will improve the instructional
practices of teachers.
Design a study for answering her question.
Address the following questions:
What are your variables? (What are will you be measuring?)
What are potential validity/alternative explanation issues with
this study?
What are the validity issues accounted for in your approach?
And how would you minimize those not accounted for in the
design?