241109 rm-j.p.-non experimental design
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Nonexperimental Nonexperimental Design-an overviewDesign-an overview
ByByDr. Jayarani PremkumarDr. Jayarani Premkumar
Professor & HeadProfessor & HeadMedical Nursing DepartmentMedical Nursing Department
College of NursingCollege of NursingCMC, VelloreCMC, Vellore
IntroductionIntroduction
Research DesignResearch Design
Research design is a set of decisions that Research design is a set of decisions that make up the master plan specifying the make up the master plan specifying the methods and procedures for collecting methods and procedures for collecting and analyzing the needed informationand analyzing the needed information
Design chosen Design chosen depends ondepends on
•Type of problemType of problem•Knowledge already available Knowledge already available about the problemabout the problem•Resources available for the Resources available for the studystudy
A Continuum of Quantitative A Continuum of Quantitative Research Design Research Design
l_____________l_____________ll_____________l_____________lNon-experimentalQuasi-experimentalExperimental
Purposes of Non Purposes of Non experimentaltal research experimentaltal research
designdesignExploration and description of Exploration and description of
phenomena in real life situationsphenomena in real life situationsUsed to develop theory Used to develop theory Identify problemsIdentify problemsMake decisions /determine what Make decisions /determine what
others in similar situations are others in similar situations are doingdoing
Critical Thinking Decision Path: Non Critical Thinking Decision Path: Non experimental Design Choiceexperimental Design Choice
Classification of Classification of Non Experimental Non Experimental
designsdesigns:: Descriptive/exploratory survey studiesDescriptive/exploratory survey studies Interrelationship/differenceInterrelationship/difference
Correlational studiesCorrelational studies Ex post facto studiesEx post facto studies Prediction studiesPrediction studies Developmental studiesDevelopmental studies
Cross-sectional & longitudinal Cross-sectional & longitudinal studiesstudies
Retrospective & prospective Retrospective & prospective studiesstudies
Descriptive researchDescriptive research
Descriptive research provides answers Descriptive research provides answers to the questions of:to the questions of:WhoWhoWhatWhatWhereWhereWhenWhenHowHow
Cannot answer the question Cannot answer the question Why?Why? conclusivelyconclusively
Reasons for Undertaking Reasons for Undertaking Non-experimental Non-experimental
StudiesStudies Number of human characteristics/ Number of human characteristics/
independent variables are not subject independent variables are not subject to experimental manipulation or to experimental manipulation or randomizationrandomization
Some variables cannot ethically be Some variables cannot ethically be manipulatedmanipulated
For some research, it is not practical to For some research, it is not practical to conduct a true experiment/manipulate conduct a true experiment/manipulate variablesvariables
Reasons -Cont’dReasons -Cont’d
For some situations, it is more For some situations, it is more realistic to explore phenomena realistic to explore phenomena in more natural mannerin more natural manner
Non-experimental research is Non-experimental research is often needed to scope out the often needed to scope out the experimental oneexperimental one
Key CharacteristicsKey Characteristics
A research design in which a A research design in which a researcher observes a researcher observes a phenomenon without phenomenon without manipulating the independent manipulating the independent variables (s)variables (s)
No manipulationNo manipulation
Key Characteristics-Key Characteristics-cont’dcont’d
Independent variables have Independent variables have already occurred, so no already occurred, so no control over themcontrol over them
Clear, concise problem Clear, concise problem statement that is based on a statement that is based on a theoretical framework, or theoretical framework, or natural phenomenon.natural phenomenon.
Descriptive ResearchDescriptive Research
Types:Types:Descriptive Correlational Descriptive Correlational
StudiesStudiesUnivariate Descriptive StudiesUnivariate Descriptive Studies
Prevalence StudiesPrevalence StudiesIncidence StudiesIncidence Studies
Descriptive ResearchDescriptive Research Purpose is to Purpose is to
observe, describe, & document observe, describe, & document aspects of a situation as it aspects of a situation as it naturally occursnaturally occurs
serve as a starting point for serve as a starting point for hypothesis generation or theory hypothesis generation or theory developmentdevelopment
Descriptive/Exploratory SurveyDescriptive/Exploratory Survey Broadest categoryBroadest category Detailed observations, descriptions Detailed observations, descriptions
& documentation of existing & documentation of existing variables variables
Little is known about the Little is known about the phenomenonphenomenon
Justifies, assesses current Justifies, assesses current conditions/practiceconditions/practice
Variables of interest: opinions, Variables of interest: opinions, attitudes or factsattitudes or facts
Descriptive/Exploratory Survey-Descriptive/Exploratory Survey-cont’dcont’d
Data collected by questionnaire Data collected by questionnaire or interviewor interview
Determines differences between Determines differences between variablesvariables
Researchers only relate one Researchers only relate one variable to another, no attempt variable to another, no attempt to determineto determine causationcausation
Exploratory Survey ResearchExploratory Survey Research
Designed to obtain information Designed to obtain information about :about : prevalence prevalence distribution distribution interrelations of variables interrelations of variables
within a populationwithin a population Census vs. sample surveysCensus vs. sample surveys
Exploratory Survey Research-cont’dExploratory Survey Research-cont’d
• Self-reportingSelf-reporting• Flexibility and broadness Flexibility and broadness • Superficiality – extensive vs. Superficiality – extensive vs.
intensive analysisintensive analysis
Descriptive survey consists of Descriptive survey consists of four major stagesfour major stages
•Selecting an appropriate Selecting an appropriate samplesample•Planning and developing Planning and developing instrumentationinstrumentation•Administering the instrument Administering the instrument and data collectionand data collection•Analysing the findingsAnalysing the findings
Descriptive/Exploratory Descriptive/Exploratory Survey (cont’d)Survey (cont’d)
Advantages: Advantages: • large amount of information can be large amount of information can be obtained from a large population in anobtained from a large population in aneconomical manner which is economical manner which is
“surprisingly” accurate“surprisingly” accurate Survey content is flexible and scope is Survey content is flexible and scope is
broadbroad
Advantages cont’d Advantages cont’d
•Subjects have greater sense of Subjects have greater sense of anonymity and may respond with anonymity and may respond with more honestymore honesty•Questions are predetermined and Questions are predetermined and standardized for all subjects, standardized for all subjects, minimizing research biasminimizing research bias•Large sample sizes are possibleLarge sample sizes are possible•A large volume of data can be A large volume of data can be collectedcollected
Descriptive/Exploratory Descriptive/Exploratory Survey (cont’d)Survey (cont’d)
DisadvantagesDisadvantages Information tends to be superficial Information tends to be superficial
as breadth is emphasizedas breadth is emphasized
Expertise in: sampling techniques, Expertise in: sampling techniques, questionnaire construction, questionnaire construction, interviewing and data analysis to interviewing and data analysis to produce a reliable and valid study.produce a reliable and valid study.
Time-consuming & sometimes costlyTime-consuming & sometimes costly
A strong descriptive design A strong descriptive design should:should:
•Include procedures that enhance the probability of generating trust worthy data
•Demonstrate appropriateness for the purpose of the study
•Be feasible given the resource available to the researcher and existing constraints
•Incorporate steps that are effective in reducing threats to validity
Univariate Descriptive Univariate Descriptive StudiesStudies
Could focus on one or more Could focus on one or more variablesvariables
Undertaken to describe the Undertaken to describe the frequency of occurrence of a frequency of occurrence of a behavior or condition or each behavior or condition or each variable rather than relationships variable rather than relationships between or among thembetween or among them
Types:Types: Prevalence StudiesPrevalence Studies Incidence StudiesIncidence Studies
Prevalence StudiesPrevalence Studies Done to determine the prevalence rate Done to determine the prevalence rate
of some condition at a specific point in of some condition at a specific point in timetime
Data is obtained from the population at Data is obtained from the population at risk for the condition – cross sectional risk for the condition – cross sectional designdesign
Prevalence Rate (PR) = Prevalence Rate (PR) = # cases with # cases with condition condition X X KK
# in population at risk # in population at risk
Incidence StudiesIncidence Studies
Used to measure the frequency of Used to measure the frequency of developing new casesdeveloping new cases
Need longitudinal designsNeed longitudinal designs
Incidence Rate (IR)= Incidence Rate (IR)= # new cases with condition over given # new cases with condition over given period period X X KK# at risk of becoming a new case# at risk of becoming a new case
Incidence Studies-cont’dIncidence Studies-cont’d
Relative Risk: Relative Risk:
an estimate of risk of an estimate of risk of “caseness” in one group vs. “caseness” in one group vs. another; another;
contribution of risk factors contribution of risk factors E.g. males vs females for E.g. males vs females for
acquiring depressionacquiring depression
Interrelationship/Difference Interrelationship/Difference Studies:Studies:
Ex Post Facto Studies Ex Post Facto Studies Literally means ‘from after the Literally means ‘from after the
fact’fact’ Also known as causal-comparative Also known as causal-comparative
studies or comparative studiesstudies or comparative studies Explores differences/relationships Explores differences/relationships
between variables (similar to between variables (similar to quasi-experimental designs)quasi-experimental designs)
Ex Post Facto Studies-Ex Post Facto Studies-cont’dcont’d
Advantages:Advantages:Allows for establishment of a Allows for establishment of a
differential effect differential effect Similar to correlational designsSimilar to correlational designsOffers a higher level of controlOffers a higher level of control
Ex Post Facto-cont’dEx Post Facto-cont’d
Disadvantages:Disadvantages:• Lack of control on variablesLack of control on variables• Unable to draw causal Unable to draw causal
linkagelinkage• Problem of alternative Problem of alternative
hypothesishypothesis
Comparative descriptive Comparative descriptive designdesign
Group 1 Group 1
(variables(variables
measured)measured)Describe
Group ii(Variables measured)
Comparison ofGroups on
Selected variables
Describe
Development Of hypothesis
DescribeInterpretation
Of meaning
Interrelationship/Difference Studies:Interrelationship/Difference Studies: Correlational Studies Correlational Studies
Examines if variables co varyExamines if variables co vary Quantifies the strength or relationship Quantifies the strength or relationship
between the variables (between the variables (notnot cause & cause & effect)effect)
+ve or –ve direction relationship +ve or –ve direction relationship determineddetermined
Correlational StudiesCorrelational Studies
Advantages:Advantages:• Increased flexibility when investigating complex Increased flexibility when investigating complex
relationships among variablesrelationships among variables• Efficient and effective method of collecting a Efficient and effective method of collecting a
large amount of datalarge amount of data• Potential for practical application in clinical Potential for practical application in clinical
settingssettings
Advantages-cont’dAdvantages-cont’d
•Potential foundation for future, experimental studies
•Framework for exploring relationships that are not manipulated.
Correlational Studies -Correlational Studies -Cont’dCont’d
DisadvantagesDisadvantages::• Unable to manipulate variable of Unable to manipulate variable of
interestinterest• No randomization in samplingNo randomization in sampling• Generalizability decreased as dealing Generalizability decreased as dealing
with preexisting groupswith preexisting groups• Unable to determine a causal Unable to determine a causal
relationship because of the lack of relationship because of the lack of manipulation, control and manipulation, control and randomization.randomization.
Descriptive Correlational Descriptive Correlational StudiesStudies
Describes the relationship Describes the relationship among variables rather than among variables rather than infer cause-and-effect infer cause-and-effect relationshipsrelationships
Are usually cross-sectionalAre usually cross-sectional
Interrelationship/Difference Studies:Interrelationship/Difference Studies: Developmental Studies Developmental Studies
Not only concerned with existing Not only concerned with existing status & interrelationship of status & interrelationship of phenomena but also with changes phenomena but also with changes from elapsed time.from elapsed time.
Cross sectionalCross sectional -one/more time -one/more time points, perhaps different groups points, perhaps different groups
Longitudinal Longitudinal :several time points :several time points with same group over extended with same group over extended period period
Developmental Studies-Developmental Studies-cont’dcont’d
Retrospective :Retrospective :dependent dependent variable has already been variable has already been affected by independent affected by independent variable & link present events variable & link present events to past eventsto past events
Prospective :Prospective :link present events link present events to presumed future effect,to presumed future effect,
less common, less common, considered stronger designconsidered stronger design
Longitudinal /prospective Longitudinal /prospective studiesstudies
Data is collected from the same Data is collected from the same group at different points in timegroup at different points in time
It explores differences and It explores differences and relationshipsrelationships
It is also referred to as repeated It is also referred to as repeated measures or cohort studiesmeasures or cohort studies
Time 1Measure variables
Sample 1
Time 2Measure variables
Sample2
Time 3Measure variables
Sample3
Strength of Longitudinal Strength of Longitudinal studiesstudies
•Capture historical trends and explore Capture historical trends and explore causal associationscausal associations
•Retrospective studies are cost effective Retrospective studies are cost effective and cost –efficientand cost –efficient
•Prospective studies can document that a Prospective studies can document that a causal factor precedes an outcome, causal factor precedes an outcome,
strengthening hypothesis about causalitystrengthening hypothesis about causality•Prospective studies provide the Prospective studies provide the
opportunity to measure characteristics opportunity to measure characteristics and events accurately and do not relay on and events accurately and do not relay on
recallrecall
Limitations of longitudinal studiesLimitations of longitudinal studies
•Attrition rates and the potential Attrition rates and the potential loss of subjects over timeloss of subjects over time•Dependent on accurate, complete Dependent on accurate, complete secondary data or the subjects secondary data or the subjects ability to recall past eventsability to recall past events•Expensive Expensive •Conclusions may be based on a Conclusions may be based on a limited number of observationslimited number of observations
CASE (S) STUDYCASE (S) STUDY
The researcher will take a case (s) The researcher will take a case (s) study and analyze in depth study and analyze in depth
Relate to other factors Relate to other factors
Improves details and understanding Improves details and understanding of causes and effect but lacks of causes and effect but lacks generalization.generalization.
Strengths of case studiesStrengths of case studies
•Provide in depth information Provide in depth information about the unique nature of about the unique nature of individualsindividuals•Responses and changes emerge Responses and changes emerge over time can be captured and over time can be captured and appraisedappraised•New insights can be obtained and New insights can be obtained and potentially generate additional potentially generate additional studiesstudies
Limitations of case studiesLimitations of case studies
•No baseline measurement to No baseline measurement to provide comparison with the provide comparison with the intervention outcomeintervention outcome•Difficult to determine if there is Difficult to determine if there is an improvement in outcomean improvement in outcome•Researcher objectivity is Researcher objectivity is requiredrequired•Results cannot be generalized to Results cannot be generalized to larger populationslarger populations
Epidemiologic Research Epidemiologic Research DesignsDesigns
Cohort studiesCohort studies::
Is a trend study in which specific Is a trend study in which specific subpopulations (e.g. age subpopulations (e.g. age specific) are examined over specific) are examined over time for generational time for generational differencesdifferences• prospective & retrospectiveprospective & retrospective
Epidemiologic Research Designs-Epidemiologic Research Designs-cont’dcont’d
Case-control studyCase-control study:: comparison of comparison of cases/subjects (with specific cases/subjects (with specific condition), with controls (without condition), with controls (without condition); only difference should be condition); only difference should be exposure to presumed causeexposure to presumed cause
Cross-sectional designCross-sectional design:: phenomena phenomena under study are captured during under study are captured during one period of data collection; one one period of data collection; one point in timepoint in time
Other designsOther designs
Natural ExperimentsNatural Experiments::
study of a group exposed to natural study of a group exposed to natural or other phenomenon that have or other phenomenon that have health or other consequences, health or other consequences, compared with a nonexposed compared with a nonexposed group; people are affected at group; people are affected at randomrandom
Others-cont’dOthers-cont’d
Path Analytic StudiesPath Analytic Studies: : using a technique called path using a technique called path
analysis, non experimental data analysis, non experimental data is tested against a hypothesized is tested against a hypothesized causal inferencecausal inference
Social class
Family Size
School Achievement
Ability
Self esteem
e1
e2
e3
Example of Path Analysis
Continuum of designs for Continuum of designs for inferring causalityinferring causality
StrongestStrongest WeakestWeakest
DesignDesign Non Experimental DesignsNon Experimental Designs DesignDesign
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Finding from descriptive studies can be used to support
Assessment of patients and patient care
Diagnosis of patient care conditions
Care planningNursing interventionsEvaluation of outcomes
SummarySummary
The purpose of descriptive research The purpose of descriptive research is the exploration and description of is the exploration and description of phenomena in real life situationphenomena in real life situation
Is used to develop theory, identify Is used to develop theory, identify problems ,provide information for problems ,provide information for decision making decision making
Summary-cont’dSummary-cont’d Nonexperimental research is research Nonexperimental research is research
that lacks manipulation of the that lacks manipulation of the independent variable by the researcherindependent variable by the researcher
The researcher studies what naturally The researcher studies what naturally occurs or has already occurred occurs or has already occurred
The researcher studies how variables The researcher studies how variables are related. are related.
Despite its limitations for studying Despite its limitations for studying cause and effect (compared to strong cause and effect (compared to strong experimental research), non experimental research), non experimental research is very important experimental research is very important in education. in education.
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