Johns Hopkins Nursing Evidence-Based Practice Thrid Edition: Model and Guidelines

(^126) Johns Hopkins Nursing Evidence-Based Practice: Model and Guidelines, Third Edition
External Validity
External validity refers to the likelihood that conclusions about research findings
can be generalized to other settings or samples. External validity is a major con-
cern with EBP when translating research into a real-world, clinical setting. An EBP
team should question the degree to which study conclusions may reasonably hold
true for its particular patient population and setting. Do the investigators state the
participation rates of subjects and settings? Do they explain the intended target
audience for the intervention or treatment? How representative is the sample of
the population of interest?
Two strategies can improve the external validity of a research study: Ensure the
representativeness of the study participants, and replicate the study in multiple
sites that differ in dimensions such as size, setting, and staff skill set. If results
are similar across these sites, this strengthens the external validity. The American
Nurses Credentialing Center (ANCC) sponsors multisite studies in Magnet
hospitals to foster participation in rigorous, large-scale research studies that con-
tribute to nursing science. Information about the studies can be found at http://
http://www.nursecredentialing.org/MagnetMultisiteStudyFAQ#researchteam-agreement.
Experimental studies are often high in internal validity because they are structured
and control for extraneous variables. However, because of this, the generalizabil-
ity of the results (external validity) may be limited. In contrast, nonexperimental
and observational studies may be high in generalizability because the studies are
conducted in real-world settings, but they are low on internal validity because of
inability to control variables that may affect the results.
Measures of internal validity include content validity, construct validity, and cross
cultural validity.
Content Validity
Content validity is the extent to which an instrument’s content adequately mea-
sures a construct—whether an instrument has an appropriate sample of items
for the construct being measured (Polit & Beck, 2017). An instrument’s content
validity is based on judgment. A panel of experts is often used to evaluate the