N4325 Nursing Research
Instructions to the student: The reading worksheets are designed to assist you as you review the
assigned readings in your Grove and Gray (2019) textbook for this module. Read the assigned pages
below and answer the following questions.
Chapter Nine: Examining Populations and Samples in Research
Samples, samples, samples! If you don’t understand the way researchers get their subjects, how will you
know if you can generalize the results to your area or unit? Chapter Nine will help you to unlock the
secrets of examining populations and samples in the research articles you are reading so that they will
make more sense to you.
What is the difference between sample, sampling, and sampling plan or sampling method?
o Sampling involves selecting a group of people, events, objects or other elements to
conduct a study
o Sampling method defines the selection process
o Sample defines the selected group of people or elements
Define the following terms: population, target population, and accessible population.
o Population is a particular group of individuals or elements who are the focus of the
research
ex: type 2 diabetics
o Target population is the entire set of individuals or elements who meet the sampling
criteria
ex: female, 18 years and older, new onset of diabetes and not on insulin
o accessible population is the portion of the target population to which the researcher has
reasonable access, certain elements within a country, state, city, hospital
ex: individuals with diabetes who were provided care in primary clinics in
Arlington, Texas
Qualitative studies call the people who participate in them subjects or participants, quantitative
studies are more likely to identify them as participants.
What is generalization and why is it important?
o Extends the findings from the sample under study to the larger population, it can
generalize the findings to the generalized population with high quality studies
Your book explains the concept of sampling or eligibility criteria. What are inclusion and
exclusion sampling criteria? Why is it important to understand these in a research study that you
are reviewing?
o Sampling or eligibility criteria include list of characteristics essential for eligibility or
membership in the target population
Module f2019 rev.
, Inclusion sampling criteria are characteristics that the subject or element must
possess to be part of the target population
Age 18 years and older, must speak and read English and surgical
replacement of one knee joint
Exclusion sampling criteria are characteristics that can cause a person or
element to be excluded from the target population
History of previous joint replacement surgery, dementia, chronic muscle
disease
Describe representativeness of a sample.
o The sample, accessible population, and target population are alike
o The setting of the study does influence the representativeness of the sample
What is the difference between random variation and systematic variation in a subject’s values?
If you were a nurse researcher, which one of these do you think you would like to avoid in your
study if possible (because it introduces bias)?
o Random variation is the expected difference in values that occur when different subjects
from the same sample are examined
Sample size increases, random variation decreases, improving
representativeness
o Systematic variation is a consequence of selecting subjects whose measurement values
differ in some specific way from those of the population, difference in the average
(mean) values between sample and population
What are the acceptance and refusal rates in a study? How do you calculate them? Do all
studies publish this information?
o Refusal rate percentage of subjects who declined to participate in the study and the
subject’s reasons for not participating
o Refusal rate = (number refusing participation/number meeting sampling criteria
approached) X 100%
In studies with a high acceptance rate or a low refusal rate, the chance for systematic variation is
less, and the sample is more likely to be representative of the target population (which is very
desirable in research).
What are sample attrition and retention rates? (Make sure you understand how this differs from
inclusion / exclusion and acceptance / refusal.)
o Sample attrition is the withdrawal or loss of subjects from a study that can be expressed
as a number of subjects withdrawing or a percentage
o Retention (opposite) is the number of subjects who remain and complete a study
In studies with a high retention rate, the chance for ___________ ____________ is less, and
the sample is more likely to be representative of the target population (which is very desirable in
research).
o The increased potential for systematic variation results in a sample that is less
representative of the target population
Module f2019 rev.