Page 465 - Encyclopedia of Nursing Research

432 n QuASI-ExPERIMENTAl RESEARcH

quantitative research can advance the scien- Quasi-experimental research is a use-
tific basis of nursing and provide a potent ful way to test causality in settings when
Q tool for defining and evaluating the out- it is impossible or unethical to randomly
comes of nursing care. In the future, quan- assign subjects to treatment and control
titative research will play an increasingly groups or to withhold treatment from some
valuable role in nursing effectiveness stud- subjects. The main disadvantage of quasi-
ies. The randomized clinical trial method, experimental research is the increased threat
perhaps the most quantitative of all research to internal validity (see Experimental Research
methods, will find increasing application for a review of types of design validity).
in nursing as attempts are made to deter- Within quasi-experimental designs, a dis-
mine the efficacy of nursing interventions. tinction is made between preexperimental,
clinically oriented research using methods nonequivalent control group designs and
such as randomized clinical trials requires interrupted time series designs. Note also
development of quantitative outcome mea- that the boundaries between experimen-
sures of variables such as quality of care tal and quasi-experimental research have
and quality of life. This will stimulate quan- blurred. Often, investigators like to define
titative research to provide the needed mea- their study as experimental when in fact it
sures and indicators. As more replications of is quasi-experimental.
quantitative nursing research become avail- Preexperimental designs are the weak-
able, the research synthesis techniques of est of the quasi-experimental designs.
meta-analysis will be increasingly applied They may lack a control or comparison
to expand nursing’s knowledge base. group, observation before the intervention
(commonly known as pretests), or both. Their
Eugene Levine use is strongly discouraged because they
do not permit even remote inferences about
the direction and dynamics of change and
causality.
Quasi-expeRimental Nonequivalent control group designs
refer to situations in which naturally occur-
ReseaRch ring groups of subjects are used as a control
or comparison group or situations in which
it is impossible or unethical to withhold
under Experimental Research in this encyclo- treatment from a given group. Despite the
pedia, the definition of cook and campell absence of randomization, nonequivalent
(1979) that experiments are character- control group designs can be considered rel-
ized by manipulation, control, and ran- atively strong designs. The use of a control
domization was cited. However, when group and a pretest significantly increase
conducting research in field settings, it is the strength of nonequivalent control group
not always possible to implement a study designs. Good pretest data will enable the
design that meets these three criteria. researcher to improve the level of analysis.
Quasi-experimental research is similar When subjects from different settings are
to experimental research in that there is used, a nonequivalent control group design
manipulation of an independent variable. It may control some threats to internal validity,
differs from experimental research because such as compensatory rivalry and demor-
either there is no control group, no random alization of controls. When subjects in each
selection, no random assignment, and/or group are naturally kept separate, it is less
no active manipulation. likely that they will have contact with each