Evidence-Based Practice for Nurses

the study indicated that the mothers in the intervention

group knew more about breastfeeding than the mothers

in the comparison group, can the researcher conclude that

the intervention was the cause of the increased knowledge?

It is possible there were other factors, such as previous

positive experiences with breastfeeding, increased fam-

ily support, and encouragement to breastfeed by nursing

staff, that were more influential in determining the results.

Given that there could be many threats to internal validity, nurses should be

cautious about changing practice based on data from preexperimental designs.

FYI

Quasi-experimental designs lack an essential

component of experimental designs. There

are several types including nonequivalent

control group pretest-posttest, one-group

time series, and preexperimental designs.

1. Quasi-experimental designs include which of the following essential components?
   a. Randomization, control group, and manipulation of the IV
   b. Randomization and control group
   c. Manipulation of the IV
   d. Randomization and manipulation of the IV


2. Experimental designs have control groups. Quasi-experimental designs have which of the
   following?
   a. Control groups
   b. Comparison groups
   c. Extraneous groups
   d. Peer groups


3. Rank the evidence generated from the following designs from lowest to highest.
   a. Experimental designs
   b. Nonequivalent control group pretest-posttest
   c. One-group posttest-only
   d. Nonequivalent-groups posttest-only

TEST YOUR KNOWLEDGE 7-2

How did you do? 1. c; 2. b; 3. c, d, b, a

7.3 Nonexperimental Designs

At the end of this section, you will be able to:

‹Describe the purpose of nonexperimental designs

‹Identify major nonexperimental quantitative designs

‹Discuss the advantages and disadvantages of various nonexperimental designs

180 CHAPTER 7 Quantitative Designs: Using Numbers to Provide Evidence