Evidence-Based Practice for Nurses

case control studies include the potential for confounding variables, bias (recall

and selection), and difficulty in selecting the control group.

Descriptive studies aim to provide information about a phenomenon. They

are nonexperimental in design and most often lack an independent variable.

They are often used when little is known about the phenomenon. Correlational

and survey designs fall into this category of research. These types of studies may

have large or small samples, be cross-sectional or longitudinal, and typically

report means, standard deviations, and frequencies. Correlations are reported

if the purpose of the study is to determine relationships.

Qualitative Designs

Qualitative nursing research provides a valuable contribution to building nurs-

ing theory and understanding the practice of nursing. Qualitative studies have

not been highly regarded in the growing field of EBP. Traditionally, it has been

difficult for many individuals to accept qualitative findings because the criteria

to determine scientific rigor are so different from the criteria for quantitative

methods. However, the contributions of qualitative research should not be

underestimated because findings provide the patient perspective, which is an

important component of EBP.

When nurses appraise qualitative studies, they should evaluate several

characteristics. The qualitative method selected should be appropriate for the

research question. Unlike quantitative research, samples tend to be small, and

nurses should determine that researchers report reaching saturation. Scientific

rigor should be maintained through orderly and detailed data collection. Strong

evidence is generated when analyses are systematic, rigorous, and auditable

(Thorne, 2000). Conclusions should be grounded in the data.

Ranking the Evidence

Decisions should not be based on one piece of evidence. Nurses need to examine

all the evidence to make recommendations about practice changes. You may

think that this will be difficult to do; however, it is usually easier than apprais-

ing an individual study. There are predetermined scales, known as evidence

hierarchies, that guide decisions for ranking studies. Because authors are

typically very clear in their descriptions of their studies,

it is usually easy to rank the evidence correctly. In EBP,

there are a variety of ways to rate evidence. These rating

systems have been designed by professional organizations

or expert panels. Figure 15-1 provides a rating system

that is commonly used in nursing to make decisions

about evidence.

KEY TERMS

descriptive studies:

Nonexperimental

studies used

to provide

information about a

phenomenon

evidence

hierarchies:

Predetermined

scales that guide

decisions for

ranking evidence;

levels of evidence

FYI

There are five steps for evaluating and imple-

menting EBP: ask, acquire, appraise, apply,

and assess. Nurses need to examine all the

evidence to make recommendations about

practice changes.

408 CHAPTER 15 Weighing In on the Evidence