Because different research strategies have different goals, they tend to have
different levels of internal validity and external validity. For example, descriptive,
correlational, and nonexperimental studies tend to examine variables in
their natural, real-world settings and, therefore, tend to have relatively good
external validity. On the other hand, experimental research tends to be rigorously
controlled and monitored and, therefore, has high internal validity.
Quasi-experimental studies tend to fall somewhere in between; they attempt
to mimic the control of true experiments, which helps internal validity, and
they tend to take place in applied, real-world situations, which helps external
validity.