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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