A good researcher is aware of these threats while planning a research study.
Anticipating threats to validity allows a researcher to incorporate elements into
a research design that eliminate or minimize threats to validity before the
research is actually conducted. In this section, we identify and briefly describe
some general threats to internal and external validity. In later chapters, we
present a variety of different research designs and consider the specific threats
to validity associated with each design. In addition, we identify methods of
modifying or expanding each design to limit specific threats to validity.
One final caution: It is essentially impossible for a single research study
to eliminate all threats to validity. Each researcher must decide which threats
are most important for the specific study and then address those threats.
Less-important threats can be ignored or treated casually. In fact, design
changes that eliminate one threat may actually increase the potential for
another threat; thus, each research study represents a set of decisions and
compromises about validity. Although researchers typically try to make the
best decisions and produce the best possible studies, most still contain some
flaws. This basic “fact of life” has two implications: