In experimental research, the researcher
examines the effects of different levels of an independent variable
on the levels of a dependent variable by manipulating the levels
of the independent variable. This feature is shared by both group-contrast
and single-subject methods.
- In group-contrast methods, the researchers manipulates the
levels of the independent variable by assigning some participating
individuals to one level of the independent variable (one condition
or treatment) and other participating individuals to another level
of the independent variable.
- In single-subject methods, the researcher manipulates the
independent variable directly by putting one level level of the
independent variable in effect for a participant and then changing
to a different level of the independent variable.
In both cases, the research compares the
level of one or more dependent variables under the various levels
of the independent variable(s).