Test 3 Flashcards
Population
Patients who share a similar characteristic, condition, disease, etc. of interest to researcher
Who is the population
Among women with breast cancer undergoing outpatient chemotherapy, how does receiving massage therapy in addition to usual care as compared to usual care only affect pain and fatigue?
POPULATION vs sample
complete set of persona or objects
Common characteristic
of interest to the researcher
population vs. SAMPLE
subset of a population
sample represents the population
Probability
- -uses random methods
- -Each element in the population has an equal, independent chance of of being selected
- -increased likelihood to yield representative sample
- -increased cost and complexity
types of probability
simple
stratified
systematic
cluster
Non-Probability
- -Random methods not used
- -Less likely to approximate target population
- -Creates a biased sample
- -increased convenience
- -decreased cost and complexity
types of Non-probability
convenience
quota
purposive
Probability sampling: simple
- -most basic form of probability
- -importance of this sampling strategy
- ——–Equal chance of selection
- ——–independent chance of selection
Advantages of SIMPLE
Little knowledge of population is needed
Most unbiased of probability method
Easy to analyze data and compute errors
Disadvantages of SIMPLE
Compete listing of population is necessary
Time consuming
Probability Sampling: STRATIFIED
- -type of probability sampling
- -population divided into subgroups or strata
- -Example of strata:
- ——gender
- ——age groups
- ——years of experience
- -Random sample taken from each strata
Proportional stratified sampling
sampling fraction for each stratum determined by proportion in total population
Disproportional stratified sampling
determine stratum is represented
used when strata are very unequal
Advantages Stratified
- -Increases probability of being representative
- -Ensures adequate number of cases for strata
Disadvantages of stratified
- -requires accurate knowledge of population
- -may be costly to prepare stratified lists
- -statistics are more complicated
Probability Sampling: Systematic
Selection of every kth case
—–selection interval determined by overall size of population divided by # needed for sample size
Example: Sample size of 100 needed from 1000 potential participants.
1000/100=10
So every 10th individual on the list is selected to create the sample of 100 people
Advantages of systematic
Easy to draw sample
Economical
Time-saving technique
Disadvantages of systematic
Samples may be biased
After first sample is chosen, no longer equal chance
Probability Sampling: Cluster
- -Larger groups or clusters, not people, are selected from population
- -Simple, stratified or systematic random sampling may be used during each phase of sampling
Advantages of Cluster
- -Saves time and money
- -Arrangements made with small number sampling units—-Characteristics of clusters or population can be estimated
Disadvantages of Clusters
- -Causes a larger sampling error
- -Requires each member assignment of population to cluster
- -Uses a more complicated statistic analysis
Nonprobability Sampling
- -Sample elements are chosen nonrandomly
- -Produces biased sample
- -Each element of the population may not be included in the sample
- -Restricts generalizations made about study findings
- -Common among nursing research studies
Advantages of nonprobability sampling
Costs less
Takes less time
Disadvantages of nonprobability sampling
Nonrandom
Not able to generalize findings
Nonprobability Sampling: convenience
- -chooses the most readily available subject or object
- -Does not guarantee that the subject or object is typical of the population
- -Snowball sampling
Snowball sampling
- -Type of convenience sampling method
- -Study subjects recruit other potential subjects
- -Also known as network sampling
- -May find people reluctant to volunteer
Nonprobabilty Sampling: Quota
- -Type of nonprobability sampling
- -Researcher selects sample to reflect characteristics
- -Examples of stratum
- —–age
- —–gender
- —–Educational background
- -Number of elements in each stratum
- —–number is in proportion to size of total population
- —–But elements not selected at random
Nonprobability sampling: purposive
- -type of nonprobability sampling
- -researcher uses personal judgment in subject selection
- -each subject chosen is considered representative of population
- -many qualitative studies use this technique
Sampling Technique to be used
- -Use voluntary subjects
- -Follow the ethics of research
- —subjects must voluntarily agree
- —subjects may refuse to participate
- -Research data
- —based on voluntary responses form subjects
- —biased sample occurs if subjects do not participate
Volunteers as Subjects
- -Participation in research is voluntary
- -Differences between volunteers and individuals approached by researcher
- —volunteers
- —questionable motivation (ex: money, other rewards)
- —May differ from those obtained via sampling (ex: greater risk-takers_
volunteers
subjects who approach the researcher asking to participate
Random sampling
each subject has equal probability of being included in the study
random assignment
Procedure to ensure that each subject has equal chance of being placed in the experimental or control group
Study Timeframe: Cross-sectional
- -subjects checked at one point in time
- -data collected from groups of people
- -data may represent differences in
- —age
- —time periods
- —developmental states
- —important considerations
Limitaitons
factors may influence internal validity of data
Study timeframe: Longitudinal
- -subjects are followed over time
- —a cohort study is one example
- -subjects are studied based on
- —similar age group
- —similar background
- -data are gathered
- —same subjects
- —several times
- -Tells influence of time
Cross-sectional
less expensive
take less time
easier to conduct
Longitudinal
Accurate means of studying changes over time
Studies take a long time to perform
Timeframe
used should be adequate to answer the study’s research question
Determining sample size
- No simple rules
- qualitative studies use much smaller samples than quantitative studies
- factors to consider for sample sizes in quantitative studies
- –homogeneity of population
- –degree of precision desired by the researcher
- –type of sampling procedure that is used
Power Analysis
- helps to determine sample size
- may prevent type II error
- helps to detect statistical significance
- —presence of a difference or correlation
- low power –> likelihood of type II error high
- external funding sources require it
- helps determine the optimum sample size
- —prevents under- or over-sampling
Nursing Research Studies
- Usually limited to small convenience samples
- Generalizations to total population difficult
- Small sample sizes warrant replication studies
- Similar results from replication help with generalization
Sampling Error
- random fluctuations in data
- not under the control of the researcher
- chance variations occur when sample is chosen
Sampling Bias
- Bias when samples are not carefully selected
- all nonprobability sampling methods have it
- may occur in probability sampling methods
- —subjects decide not to participate when chosen
- —final sample is now not representative of population
Data collection method types
questionnaire interview observation physiological measure psychological measure
data collection methods factors influencing selection
research question research method variable(s) of interest access to population availability of appropriate instruments cost timeframe
Questionnaires
- self-report
- only method for certain human response data
- –Ex: attitudes, beliefs, knowledge level
questionnaires: categories of questions
demographic open-ended closed-ended contingency filler
questionnaires: distribution
-made available at a convenient location
-through a mailing or distribution system
-through internet
========responses rate influenced by many factors
Advantages of questionnaires
- quick and generally inexpensive
- easy to test for reliability and validity
- administration is time efficient
- can obtain data from widespread geographical areas
- allows for anonymous responses
disadvantages of questionnaires
- costly to mail if large volume
- potential low response rate
- respondents give socially acceptable answers or fail to answer
- respondents may not be representative of the population
- no opportunity to clarify items for respondents
- respondents must be literate or have no physical limitation
Interview
- method of data collection
- interviewer obtains responses
- face-to-face encounter, by telephone, or through an internet connection
- QUANT and QUAL studies
Types of interviews
unstructured
structured
semi-structured
Influencing factors of interviews
face-to-face
interviewer influence
telephone interview
face-to-face interview
- ethnic background
- age
- gender
- manner of speaking
- manner of dress
Interviewer influence
- non-experimental research: Rosenthal effect
- Experimental studies: experimenter effect
Telephone interview
tone
dialect
Advantages of interviews
- high response rate
- in-depth responses
- wide range of participants
- high percentage of unstable data
- ability to observe verbal an nonverbal behavior
disadvantages of interviews
- time consuming
- expensive
- arrangements may be difficult
- participants may
- —be influenced by the interviewers’ characteristics
- —intentionally provide socially acceptable responses
- —be anxious because answers are being recorded
observation data
- data gathered through visual observation
- nurses are well qualified to use this method
- carefully developed plan is essential
Examples of observable behavior
- psychomotor skills
- personal habits
- nonverbal communication patterns
- inter-rater reliability
- —The degree to which two or more raters or observers assign the same rating or score to an observation
Structured observations
- data-collection tool, usually some kind of checklist
- expected behaviors are identified on the checklist
- observer indicates the frequency of behavior occurrence
Unstructured obervations
- researcher attempts to describe events or behaviors freely
- process requires a high degree of concentration and attention
Physiological measures
- involve the collection of physical data from subjects
- measures are objective and accurate
- Ex: lab values, weight, vital signs
- advantage–precision and accuracy
- disadvantage–expertise required for using devices
Psychological Measures
- Attitude scales (ex: attitudes, feelings)
- —-Likert scale, semantic differential scales
- Personality tests
- Visual analogue scale
- —0-10 pain scale
Visual Analogue Scale
- Presents subjects with a 100mm straight line drawn on a piece of paper
- Subjects are asked to make a mark on the line at the point that corresponds to their experience of the phenomenon
- Quantitative data is obtained from measurements of the responses
- useful for measuring: nausea, pain, fatigue, shortness of breath
Pre-existing Data
- Data is used from previous research
- Existing information is reanalyzed for new research
- Preexisting data sources
- –patient charts
- –records from agencies and organizations
- –personal documents
- –almanacs
- –professional journals
Measurement
- Process of assigning numbers to variables
- ways to assign numbers
- in research, measurement is…
- –quantification of information
- –Applied mostly in quantitative research designs
Ways of assign numbers
counting
ranking
comparing objects or events
Qualitative research designs
- Concept of measurement does not apply to qualitative data in narrative form
- concept of measurement may apply to qualitative data that is summarized an places into categories
Level of Measurement: Nominal
- lowest level of measurement
- objects or events are named or categorized
- Categories must be exhaustive and mutually exclusive
Examples of nominal level
gender
marital status
religious affiliation
Level of Measurement: Ordinal
- second level of measurement
- data can be rank ordered and placed into categories
- exact differences between rank not possible
Examples of ordinal level
mild
moderate
severe
Level of Measurement: Interval
- Third level of measurement
- data can be rank ordered and placed into categories
- Distance between ranks can be measured
- actual numbers on a scale
Level of Measurement: Ratio
- highest level of measurement
- data is categorized and ranked
- distance between ranks is “true” or natural zero
- zero means a total absence of quantity measured
- debate usually exists between interval and ratio level
Examples of ratio level
- money in bank account
- body weight
Appropriate level of meausrement
- Precision- interval or ratio
- ranked or categorized sufficient- ordinal
- categories of data only needed- nominal
level of measurement considerations
- level is appropriate for the type of data desired
- degree of precision that is desired for the study