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              RESEARCH LIMITATIONS

 It is important to gain an understanding of research limitations. Thinking
about research limitations may foster
critical thinking.  
    Every study, no matter how well it is conducted, has some limitations.
This is why it does not seem reasonable to use the words "prove" and
"disprove" with respect to research findings.  It is always possible that
future research may cast doubt on the validity of any hypothesis or the
conclusions from a study.

Limitations of Case Studies

    Case studies may be viewed as having the most limitations.  You
cannot make causal conclusions from case studies.
This is true because
we cannot rule out alternative explanations.
  
It is always unclear about the generality of the findings of a case
study.
A case study involves the behavior of one person.  The behavior of
one person may not reflect the behavior of most people.  Thus, we do not
know how others may behave.

Limitations of Correlational Studies

  Correlational research also has the same limitations as case studies.  
Correlational research merely demonstrates that we can predict a variable
from another variable.  It is demonstrating that two variables are
associated.  However, two variables can be associated without there being
a causal relationship between the variables.  
We cannot make causal
conclusions from correlational findings because we cannot rule out all
alternative explanations for correlational findings.
Thus, making causal
conclusions from correlational findings is a logical error.  If we find that A
is associated with B, it could mean that A caused B, B caused A, or some
third variable caused both A and B without there being any causal
relationship between A and B.  Even if we could rule out one of the
possible relationships (e.g., B caused A), we cannot rule out all alternative
explanations from correlational studies.  For every correlational study,
there is the possibility that some third variable caused the two variables
without there being a causal relationship between the variables.
    Correlational research may also have limitations with respect to the
generality of the findings.  Perhaps the study involved a specific group of
people, or the relation between the variables were only investigated in
some situations.  Thus, it may be uncertain whether the correlational
findings may generalize to other people or situations.

Limitations of Randomized Experiments

     
Experiments involving the random assignment of participants to
conditions may allow us to make causal conclusions if the variables that
are manipulated are not confounded with other variables.  However, there
still may be limitations with respect to the generality of the findings.  The
experiment may have involved a specific group of people, certain
situations, and only some of the possible conceptualizations of variables.  
Thus, we may not know whether the findings will generalized to other
people, situations, or conceptualizations of the variables.