Chapter 9 Selecting the Sample & Setting (Quantitative)) Flashcards
Population
A well-defined group whose members possess specific attributes
Target Population
The group being studied
-Eligibility criteria
Inclusion Criteria
The key features of the target population that the investigators will use to answer their research question
Exclusion Criteria
Features of the potential study participants who meet the inclusion criteria but present with additional characteristics that could interfere with the success of the study or increase their risk for an unfavorable outcome
Sample
Small subset of a population
Select Sample
Representative of the population
Sampling
Process of selecting individuals for a study
Probability Sampling
“Random Sampling”
Simple Random Sample
Every subject has an equal & independent chance of being chosen
Cons of Simple Random Sampling
Can be time-consuming
More pricey
Difficult, or impossible, to obtain an accurate or complete sampling frame of every element in accessible population
Stratified Random Sampling
Selecting a sample to identify subgroups in the population that are represented in the sample
Advantages of Stratified Random Sampling
Achieves greater degrees of representation w/in population
Cluster (Multistage) Sampling
Groups, not individuals, are randomly selected
Used for convenience in:
o large populations
o populations spread over large geographic area
Systematic Sampling
Individuals or elements of the
population are selected from a list by
taking every kth individual
Each member does not have an
independent chance of inclusion
Considered random sampling if list is
randomly ordered 1st
Data collected conveniently and
efficiently
Non-probability Sampling
“Non-random Sampling”
Chance plays no role in
determination of sample
Limits ability to make
generalizations about findings
Many nursing research studies use
non-probability sampling because of
difficulties in obtaining random
access to populations
Convenience Sampling
Collection of data from subjects that are readily available or easily accessible to the researcher
Advantages of Convenience Sampling
Easy to carry out
Cost-efficient
Disadvantages of Convenience Sampling
Potential for bias
Limited ability for results to be generalized
Snowball (network) Sampling
Useful when list of individuals who share particular characteristic cannot be obtained
Researchers ask subjects to help them get in touch w/other potential subjects
Quota Sampling
Identifies the strata of the population based on specific characteristics
Quota is computed proportionally or
disproportionally to the population under study
Purposive Sampling
Researcher “handpicks” or selects certain cases thought to be best representatives to be included
in the study
Commonly used in qualitative research
How do you determine sample size for quantitative study?
Have a large enough sample size to be representative of the population but, not too large not to gain sufficient information
What are quantitative studies determined by?
Power Analysis
Power Analysis
The calculation used to estimate the smallest sample size needed for an experiment, given a required significance level, statistical power, and effect size
What occurs if the sample size is too small?
Results in insufficient power to determine differences among groups
What are qualitative studies determined by?
Data Saturation
Data Saturation
The point in a research process where enough data has been collected to draw necessary conclusions, and any further data collection will not produce value-added insights
External Validity
Extent to which study results can be generalized from the study sample to other subjects, populations, measuring instruments, & settings
Threats to External Validity
Interaction of Sample & Treatment: Samples confined to certain types of subjects
Interaction of setting and treatment: Bias when members of different settings agree to participate
Interaction of history and treatment: Concerns about ability to generalize results to different periods of time in the past or future
Natural Setting
Uncontrolled, real-life situation
Partially-Controlled Setting
Manipulated or modified in some way
Highly Controlled Setting
Artificial environment for sole purpose of doing research. Decreases effects of outside influences.
Quantitative Data Collection
Numerical
Formulated into tables or counts
Analyzed without extreme effort
Data collection involves use of
instruments
Surverys
Self-admin
May be mailed or conducted face-to-face
Questionnaires
Closed-ended
Open-ended
Psychometric Assessment
Evaluates the measure’s measurement properties
Reliability
Extent to which scores are free from measurement error
Test-Retest Reliability
Admin a measure to the same people on 2 occasions
Interrater Reliability
Having 2 or more observers independently apply the measure w/ same people to determine consistency
Internal Consistency Reliability
Extent that the items measure the same trait across items on scales
Reliability Coefficient Scale
Range from .00 to 1.00 with .80 or higher is acceptable
Chodos randomly assigned 50 men and 50 women smokers (who had responded to an online recruitment notice) to a smoking cessation intervention or to a control group.
Probability or Non-probability
Non-Probability
The sample was a quota sample; men & women responded to a notice and were not selected at random
Solomons studied circadian rhythms in a sample of 45 pregnant women consecutively admitted to a hospital in the first 6 months of 2016 because of severe preeclampsia.
Probability or Non-Probability?
Non-Probability
The sample was a consecutive sample of patients meeting eligibility criteria; they were not selected at random
Kane randomly sampled 250 nurses from urban areas and 250 from nonurban areas from a roster of licensed nurses in Florida to study their attitudes toward evidence-based practice
Probability or Non-pProbability?
Probability
Marshall randomly selected 250 students from a large university to study their use of drugs and alcohol.
Probability or Non-Probability?
Probability
The sample was a simple random sample of students, presumably students were selected at random.
Rocco administered her self-efficacy scale to 50 patients twice, 1 week apart. The coefficient between the two sets of scores was .82.
Reliability or Validity?
Reliability
Rogers examined the relationship between scores on a self-report insomnia scale and sleep efficiency indexes as measured by an Actiwatch wristband.
Reliability or Validity?
Validity
Rogers was assessing criterion validity by using the Actiwatch wristband
Pfortmiller assessed the degree to which the 12 items on his resilience scale measured a unitary attribute; he calculated a coefficient of .91.
Reliability or Validity?
Reliability
Pfortmiller was assessing the internal consistency reliability of his scale.
Blalock compared scores on her Breastfeeding Anxiety Scale for two groups: women in their first pregnancy and women who were lactation consultants.
Reliability or Validity?
Validity
Blalock was using the known-groups technique to assess the construct validity of her scale.
Casey randomly assigned 152 elders recruited from 5 nursing homes
Rocco administered her self-efficacy scale to 50 patients
