Evidence-Based Practice for Nurses

When obtaining a purposive sample, researchers often use what is known as

snowball sampling, or network sampling. When using this approach, an initial

participant who meets the study criteria is identified. This participant then

identifies other individuals who meet the criteria for inclusion in the study. To

protect confidentiality, researchers must ascertain from the referring participant

that it is permissible to contact suggested potential participants. When using

snowball sampling, researchers assume that individuals will identify others

who are similar to themselves. Snowball sampling is a useful method to identify

participants who would otherwise be difficult for the researchers to find. Sup-

pose a researcher is investigating the lived experience of young women with

eating disorders. By first identifying a small group of women who meet the

criteria and then asking them to identify other young women that they know,

researchers can find a larger number of potential participants.

Theoretical Sampling

Another sampling method, used specifically in grounded theory, is theoretical

sampling. When using this sampling method, researchers collect data from an

initial group of participants. After conducting some preliminary analyses of

data, researchers identify additional participants for inclusion in the sample

(Fawcett & Garity, 2009).

1. A researcher desires to study the effect of a memory game on older adults’ abilities
   to recall a short-term task list. The researcher randomly selects 20 elders from a list of
   residents at a local nursing home. The sampling method used is
   a. convenience sampling.
   b. quota sampling.
   c. simple random sampling.
   d. purposive sampling.


2. Which of the following sampling methods involves randomization? (Select all that apply.)
   a. Systematic sampling
   b. Snowball sampling
   c. Stratified random sampling
   d. Cluster sampling


3. To use random sampling, a researcher must know the
   a. sampling frame.
   b. characteristics of the population.
   c. exclusion criteria.
   d. sampling interval.

TEST YOUR KNOWLEDGE 11-2

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

KEY TERMS

snowball sampling:

Recruitment of

participants based

on word of mouth

or referrals from

other participants

network sampling:

Recruitment of

participants based

on word of mouth

or referrals from

other participants;

snowball sampling

theoretical

sampling:

Nonprobability

sampling method

used in grounded

theory to collect

data from an

initial group of

participants

298 CHAPTER 11 Using Samples to Provide Evidence