Study Designs in reasearch

8/14/2019 Study Designs in reasearch

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Study DesignsStudy DesignsAA

PresentationPresentation


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Types of Study designsTypes of Study designs

Non Intervention StudiesNon Intervention StudiesDescriptive studiesDescriptive studies

Comparative (analytical) studiesComparative (analytical) studies

Exploratory studiesExploratory studies

Intervention StudiesIntervention Studies

The two categories of intervention studiesThe two categories of intervention studies

are:are:

Experimental studiesExperimental studies

Quasi-experimental studies.Quasi-experimental studies.


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E P I D E M I O L O G I C A L S

1 . C a s e

2 . C a s e

3 . C o r r e l a t

4 . C r o s s S e

D E S C R I

C O H

C A S E

O B S E R V

3 . T r i

2 . D o u

1 . S i n

E X P E R I M

A N A L Y T

CurrentCurrent

ClassificationClassification


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Descriptive StudiesDescriptive Studies

Descriptive studies involve theDescriptive studies involve the

systematic collection andsystematic collection and

presentation of data to give apresentation of data to give a

clear picture of a particularclear picture of a particular

situation and can be carried outsituation and can be carried out

on a small or large scale.on a small or large scale.

Case studiesCase studies

Case seriesCase series


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Comparative or AnalyticalComparative or Analytical

StudiesStudies

An ANALYTICAL STUDY attempts toAn ANALYTICAL STUDY attempts toestablish causes or risk factors forestablish causes or risk factors for

certain problems. This is done bycertain problems. This is done by

comparing two or more groups,comparing two or more groups,

some of which have or develop thesome of which have or develop the

problem and some of which haveproblem and some of which have

notnot..


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Quantify the distribution of certain variables in aQuantify the distribution of certain variables in astudy population at a point of time. They maystudy population at a point of time. They may

cover, for example:cover, for example:

Physical characteristics of people, materials, or thePhysical characteristics of people, materials, or theenvironment,etcenvironment,etc

The behavior of people and the knowledge, attitudes,The behavior of people and the knowledge, attitudes,beliefs, and opinions that may help to explain thatbeliefs, and opinions that may help to explain that

behaviour (KAP studies), or events that occurred inbehaviour (KAP studies), or events that occurred in

the population.the population.

Cross-sectional surveys cover a sample of theCross-sectional surveys cover a sample of thepopulation. If a cross-sectional study covers the totalpopulation. If a cross-sectional study covers the totalpopulation it is called a census.population it is called a census.

Cross SectionalSurveys


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Case Control StudiesCase Control Studies

In a CASE-CONTROL STUDY, theIn a CASE-CONTROL STUDY, theinvestigator compares one groupinvestigator compares one group

among whom a problem is (e.g.,among whom a problem is (e.g.,

malnutrition) with anothermalnutrition) with another

group, called a control orgroup, called a control or

comparison group, where thecomparison group, where the

problem is absent to find outproblem is absent to find outwhat factors have contributed towhat factors have contributed to

the problem.the problem.


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Cohort StudiesCohort Studies

In a COHORT STUDY, a group of individuals thatIn a COHORT STUDY, a group of individuals thatis exposed to a risk factor (study group) isis exposed to a risk factor (study group) is

compared with a group of individuals notcompared with a group of individuals not

exposed to the risk factor (control group).exposed to the risk factor (control group).

The researcher follows both groups over time andThe researcher follows both groups over time andcompares the occurrence of the problem that he or shecompares the occurrence of the problem that he or she

expects to be related to the risk factor in the two groupsexpects to be related to the risk factor in the two groups

to determine whether a greater proportion of those withto determine whether a greater proportion of those with

the risk factor are indeed affected.the risk factor are indeed affected.


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Relative Ratio (RR)Relative Ratio (RR)

Ratio of incidence of the disease (orRatio of incidence of the disease (ordeath)among exposed and thedeath)among exposed and the

incidence among non-exposed.incidence among non-exposed.

It is a direct measure (or index) ofIt is a direct measure (or index) of

the strength of the associationthe strength of the association

between suspected cause and effectbetween suspected cause and effect


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Exploratory StudiesExploratory Studies

An Exploratory study is a small-scaleAn Exploratory study is a small-scale

study of relatively short duration,study of relatively short duration,

which is carried out when little elsewhich is carried out when little elseis known about a situation or ais known about a situation or a

problem.problem.

I i


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InterventionIntervention

StudiesStudies

In intervention studies, the researcherIn intervention studies, the researchermanipulates a situation and measuresmanipulates a situation and measures

the effects of the manipulation. Usuallythe effects of the manipulation. Usually

(but not always) two groups are(but not always) two groups are

compared, one in which the interventioncompared, one in which the intervention

takes place (e.g.. treatment with atakes place (e.g.. treatment with a

certain drug) and another group thatcertain drug) and another group that

remains "untouched" (e.g., treatmentremains "untouched" (e.g., treatment

with a placebo) .with a placebo) .


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Experimental StudiesExperimental Studies

Experimental design is the only type ofExperimental design is the only type ofstudy design that can actually provestudy design that can actually prove

causation.causation.

In an EXPERIMENTAL STUDY, individuals areIn an EXPERIMENTAL STUDY, individuals are

randomly allocated to at least two groups.randomly allocated to at least two groups.

One group is subjected to an intervention orOne group is subjected to an intervention or

experiment, while the other group(s) is not.experiment, while the other group(s) is not.

The outcome of the intervention - effect of theThe outcome of the intervention - effect of theintervention on the dependentintervention on the dependent

(variable/problem) is obtained by(variable/problem) is obtained by

comparing the two groups.comparing the two groups.


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The classical experimental studyThe classical experimental study

design has threedesign has three

characteristics:characteristics:

ManipulationManipulation

ControlControlRandomizationRandomization

Classical ExperimentalStudy Design

Q i i lQ i E i t l


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Quasi ExperimentalQuasi Experimental

StudiesStudies

In a QUASI-EXPERIMENTAL STUDY,In a QUASI-EXPERIMENTAL STUDY,at least one characteristic of a trueat least one characteristic of a true

experiment is missing.experiment is missing.

One of the most common quasi-One of the most common quasi-experimental designs uses two (or more)experimental designs uses two (or more)

groups, one of, which serves a controlgroups, one of, which serves a control

group in which no intervention takesgroup in which no intervention takes

place.place.

Both groups are observed before as wellBoth groups are observed before as wellas after the intervention, to test if theas after the intervention, to test if the

intervention has made any difference.intervention has made any difference.

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Study Designs in reasearch