Saylor URL: http://www.saylor.org/books Saylor.org
- Explain how generalization, replication, and meta-analyses are used to assess the external validity of research
findings.
Good research is valid research. When research is valid, the conclusions drawn by the researcher
are legitimate. For instance, if a researcher concludes that participating in psychotherapy reduces
anxiety, or that taller people are smarter than shorter people, the research is valid only if the
therapy really works or if taller people really are smarter. Unfortunately, there are many threats
to the validity of research, and these threats may sometimes lead to unwarranted conclusions.
Often, and despite researchers’ best intentions, some of the research reported on websites as well
as in newspapers, magazines, and even scientific journals is invalid. Validity is not an all-or-
nothing proposition, which means that some research is more valid than other research. Only by
understanding the potential threats to validity will you be able to make knowledgeable decisions
about the conclusions that can or cannot be drawn from a research project. There are four major
types of threats to the validity of research, and informed consumers of research are aware of each
type.
Threats to the Validity of Research
- Threats to construct validity. Although it is claimed that the measured variables measure the conceptual
variables of interest, they actually may not. - Threats to statistical conclusion validity. Conclusions regarding the research may be incorrect because no
statistical tests were made or because the statistical tests were incorrectly interpreted. - Threats to internal validity. Although it is claimed that the independent variable caused the dependent variable,
the dependent variable actually may have been caused by a confounding variable. - Threats to external validity. Although it is claimed that the results are more general, the observed effects may
actually only be found under limited conditions or for specific groups of people. (Stangor, 2011) [1]
One threat to valid research occurs when there is a threat to construct validity.
Construct validity refers to the extent to which the variables used in the research adequately
assess the conceptual variables they were designed to measure. One requirement for construct
validity is that the measure be reliable, where reliability refers to the consistency of a measured
variable. A bathroom scale is usually reliable, because if we step on and off it a couple of times