A statistical procedure alone cannot determine casual relationships.
Rather it involves the design and measurement issues. The following is
extracted from my handout:
One of the objectives of conducting experiments is to make causal
inferences. At least three criteria need to be fulfilled to validate a
causal inference (Hoyle, 1995):
Directionality: The independent variable affects the dependent variable.
Isolation: Extraneous noise and measurement errors must be isolated from
the study so that the observed relationship cannot be explained by
something other than the proposed theory.
Association: The independent variable and the dependent variable are
mathematically correlated.
To establish the direction of variables, the researcher can apply logic
(e.g. physical height cannot cause test performance), theory (e.g.
collaboration affects group performance), and most powerfully, research
design (e.g. other competing explanations are ruled out from the
experiment).
To meet the criterion of isolation, careful measurement should be
implemented to establish validity and reliability, and to reduce
measurement errors. In addition, extraneous variance, also known as
threats against validity of experiment, must be controlled in the design
of experiment.
Last, statistical methods are used to calculate the mathematical
association among variables. However, in spite of a strong mathematical
association, the causal inference may not make sense at all if
directionality and isolation are not established.
In summary, statistics analysis is only a small part of the entire
research process. Hoyle (1995) explicitly warned that researchers should
not regard statistical procedures as the only way to establish a causal
and effect interpretation.
Hoyle, R. H.. (1995). The structural equation modeling approach: Basic
concepts and fundamental issues. In R. H. Hoyle (Eds.), Structural
equation modeling: Concepts, issues, and applications (pp. 1-15).
Thousand Oaks: Sage Publications.
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Chong-ho (Alex) Yu, Ph.D., CNE, MCSE
Instruction and Research Support
Information Technology
Arizona State University
Tempe AZ 85287-0101
Voice: (602)965-7402
Fax: (602)965-6317
Email: [EMAIL PROTECTED]
URL:http://seamonkey.ed.asu.edu/~alex/
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