an experiment in which a treatment (intervention) is implemented with a high degree of control, permitting an appropriate comparison (e.g., between the treatment and control groups) such that an unambiguous decision can b made concerning the effect of the treatment.
possible causes of a phenomenon that must be controlled so a clear cause-and -effect inference can be made.
Threats to Internal Validity
procedures that resemble the characteristics of true experiments--for example, an intervention or a treatment is used and comparison is provided--but procedures lack the degree of control found in true experiments.
a quasi-experimental method in which a comparison is made between control and treatment groups that have been established on a basis other than through random assignment of participants to groups.
Nonequivalent Control Group Design
a quasi-experimental procedure in which changes in a dependent variable are observed for a period of time both before and after a treatment is introduced.
Simple Interrupted Time-Series Design
a quasi-experimental procedure that improves the validity of a simple time-series design by including a nonequivalent control group; both treatment and comparison groups are observed for a period of time both before and after the treatment.
Time Series with Nonequivalent Control Group Design
research that seeks to determine whether a change proposed by an institution, a government agency, or another unit of society is needed and likely to have an effect as planned or, when implemented, to actually have an effect.