Evidence-Based Practice for Nurses

Type of

Sampling Assumptions

Possibility

of Bias Representativeness

Other

Comments

Convenience

sampling

1. Inclusion criteria
   identified prior
   to selection of
   subjects


2. All subjects
   are invited to
   participate

Highest

probability

of bias

Because sample

is selected for

ease of data

collection, may not

be representative

of the target

population

Seen in many

nursing

studies

because of

ease of data

collection

Quota

sampling

1. Strata must be
   mutually exclusive
   so a subject can be
   assigned to only
   one stratum


2. Convenience
   sampling used to
   select subject from
   each stratum

May have

some bias

resulting from

convenience

sampling

after strata are

identified

Because sample

within each stratum

is selected using

convenience

sampling method,

may not represent

the population

Similar to

stratified

random

sampling

except

convenience

sampling is

used to obtain

the sample in

each stratum

Purposive

sampling

1. Researcher
   has sufficient
   knowledge of topic
   to select sample
   of experts


2. Researcher
   should identify
   criteria to include
   in selection of
   subjects


3. Commonly used
   in qualitative
   research

May have

minimal bias if

identification

of participants

adheres to

selection criteria

and sample

in study is

homogenous

Because sample

is selected by

researcher,

cannot generalize

to population;

generalizing the

results is not an

expected outcome

of qualitative

research

Focus of this

research is to

learn more

about and

understand

the

phenomenon

being studied

Theoretical

sampling

1. Data collection
   and data
   analysis occur
   simultaneously


2. Commonly used in
   grounded theory
   research

Not applicable

with this type

of sampling

Cannot generalize

to population;

generalizing the

results is not an

expected outcome

of grounded theory

research

Used in

grounded

theory

Data from Gray, J., Grove, S., & Sutherland, S. (2016). Burns and Grove’s the practice of nursing

research: Appraisal, synthesis, and generation of evidence (8th ed.). St. Louis, MO: Saunders;

Polit, D., & Beck, C. T. (2014). Essentials of nursing research: Appraising evidence for nursing

practice. Philadelphia, PA: Lippincott Williams & Wilkins.

TABLE 11-3 Overview of Nonprobability Sampling

296 CHAPTER 11 Using Samples to Provide Evidence