(^108) Johns Hopkins Nursing Evidence-Based Practice: Model and Guidelines, Third Edition
Nonexperimental Studies
Similar to experimental research designs, nonexperimental research designs are
the blueprint for all aspects needed to carry out the study—overall for the col-
lection, measurement, and analysis of data. When reviewing evidence related to
healthcare questions, particularly inquiries of interest to nursing, EBP teams will
often find studies of naturally occurring phenomena (groups, treatments, and
individuals). These studies are considered nonexperimental or observational in
design. The studies may or may not introduce an intervention. Subjects are not
randomly assigned to different groups, variables are not manipulated, and the in-
vestigator is not always able to control aspects of the environment.
Quantitative nonexperimental studies can be classified by research purpose and
by time dimension (Belli, 2009). Three categories classified by purpose, or intent,
are descriptive, predictive, and explanatory. Categories classified by time are pro-
spective, longitudinal, and retrospective.Descriptive Designs
The intent of purely descriptive designs, as the name implies, is to describe or
identify situations or characteristics of phenomena. Basic questions asked in de-
scriptive research are: What are the quantifiable values of particular variables
for a given set of subjects? How widespread is a phenomenon? Variables are
not manipulated, and no attempt is made to determine that a particular interven-
tion or characteristic is related to or causes a specific occurrence to happen.Examples: Quasi-Experimental Studies
Labrague and McEnroe-Petitte (2014) conducted a study to determine the
influence of music on anxiety levels and physiologic parameters in women
undergoing gynecologic surgery. The study used a pretest and posttest
experimental design with nonrandom assignment to control group (nonmusic
group) or experimental group (music group). The study is quasi-experimental
rather than purely experimental; although it included a music intervention
(manipulation) and no music (control), the subjects were not randomly assigned
to each group.