Evidence-Based Practice for Nurses

XO XO

XO XO

XO

XO

XX

XX

XO

XO

Population

Representative

sample

Unrepresentative

sample

FIGURE 11-2

Representative vs. Unrepresentative

Samples

1. Define and clearly articulate the target population for the study by listing all of the essential
   characteristics of the target population or eligibility criteria for inclusion in the study.


2. Identify the population the researcher has access to for the study, taking care to verify that the
   accessible population closely resembles the target population by using the same eligibility
   criteria.


3. Develop a method to approach the accessible population. Some researchers refer to this
   as a sampling frame. The sampling frame is a practical method used to gain access to the
   population that is readily available to the researcher.


4. Select subjects from the accessible population to include in the sample.
   Modified from Melnyk, B. M., & Cole, R. (2011). Generating evidence through quantitative research.
   In B. Melnyk & E. Fineout-Overholt (Eds.), Evidence-based practice in nursing and healthcare
   (2nd ed., pp. 397–434). Philadelphia, PA: Lippincott Williams & Wilkins.

BOX 11-1 Four Steps to Ensure Representative Samples

Researchers may also designate exclusion criteria, which are characteristics

of elements that will not be included in a sample. The use of exclusion criteria

may decrease the risks of certain characteristics influencing the results of a

study (Bloom & Trice, 2011). For example, the researcher wants to study cop-

ing in adolescents with type 1 diabetes. Individuals having another chronic

KEY TERM

exclusion criteria:

Characteristics of

elements that will

not be included in

the sample

288 CHAPTER 11 Using Samples to Provide Evidence