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RESEARCH DESIGN

K. SYED ABUDAHEER, M.P.T.,

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´ A research design is the arrangement of conditions for

collection and analysis of data in a manner that aims to

combine relevance to the research purpose with economy

in procedure. (Claire Selltiz, 1962)

´ The research is the plan, structure, and strategy of

investigations of answering the research question is the

overall plan or blueprint the researchers select to carry our

their study.

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´ Research design is always gives the answers of following

questions

« What is the study about ?

« Why is the study being made ?

« Where will the study be carried out ?

« What type of data is required ?

« Where can the required data be found ?

« What periods of time will the study include ?

« What will the sample design ?

« How will the data be analyzed ?

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NEED FOR RESEARCH DESIGN

´ Minimizes time and money

´ Advance planning

´ Avoid flaws

´ Selection of appropriate tools

´ Eliminate bias and marginal error

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FEATURES OF GOOD DESIGN

´ It should be flexible, appropriate, efficient, economical andso on.

´ It should give a smallest experimental error and high

reliability and validity.

´ Good research design includes following five important

elements.

« Subjects

« Variables

« Time

« Setting

« Investigator·s role

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PRINCIPLES OF RESEARCH DESIGN

Professor Fisher has enumerated three important principles of research design.

´ Principle of Replication

´ Principle of randomization

´ Principle of Local Control

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PRINCIPLE OF REPLICATION

´ According to this principle, the experiment should be

repeated more than once. Thus, each treatment is applied

in many experimental units instead of one.

´ By doing this method, the accuracy and precision of the

study are increased significantly.´ For example, the effect of two variety of rice.

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PRINCIPLE OF RANDOMIZATION

´ This principle provides protection

´ This principle indicates that the researcher should design or

plan the experiment in such a way that the variations

caused by extraneous factors can all be combined under

the general heading of ´Chanceµ.´ Example : effect of two variety of rice

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PRINCIPLE OF LOCAL CONTROL

´ The extraneous factors, the know source of variability, is

made to vary deliberately over as wide a range as

necessary and this needs to be done in such a way that the

variability it causes can ne measured and hence eliminated

from the experimental error.´ Example : effect of two variety of rice

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TYPES OF RESEARCH DESIGN

´ Experimental design - which obey the all

three principles.

´

Quasi ²Experimental design´ Non- experimental design

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EXPERIMENTAL DESIGN

´ The investigator planning an experiment has manyexperimental design option to choose. Experimental

designs fall into two major categories.

« True or Classical experimental design« Pre- experimental design

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TRUE OR CLASSICAL EXPERIMENTAL DESIGN

´ There are three major subdivisions in true or classicalexperimental design

« Pre test ² post test control group design

«

Solomon four group design« After / post test only experimental design

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PRE TEST ± POST TEST CONTROL GROUP DESIGN

´

Experimental group

experimental treatment

Pre test Post test

´ Control group

Pre test Post test

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PRE TEST ± POST TEST CONTROL

GROUP DESIGN

´ In this design, subjects have been designed randomly to theexperimental or control group

´ The experimental treatment is given only to those in the

experimental group, and the pre tests and post tests are

those measurements of the dependent variables that aremade before and after the experimental treatment is

performed.

´ All true experimental designs have subjects randomly

assigned groups, have an experimental treatment

introduced to some of the subjects and have the effects of

the treatment observed.

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´ The investigator is able to account for events occurring between time 1 and time 2 through observation of control

group

´ It also enables the investigator to control for changes in theinstrumentation, since changes or drifts in measurement

should affect both groups equally

´ Randomization decreases selection bias and maturation.

ADVANTAGES

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SOLOMON FOUR GROUP DESIGN

´

Experimental groupI


Pre test Post test

´ Control group I

Pre test Post test

´ Experimental group IIexperimental treatment

Post test

´ Control group II

Post test

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SOLOMON FOUR GROUP DESIGN

´ This design employs two experimental groups and twocontrol groups. Initially, the investigator randomly assigns

subjects to the four groups. Those in the first experimental

treatment, and observed again on occasion 2.

´ Those in the experimental group 2 also receive the

treatment but are observed only after the treatment, nor

before.

´ Those in control group 1 are observed, on occasion 1 and

2, but they are not given the experimental treatment.

´ Those in control group 2 are observed only on the second

occasion without previous observation or treatment.

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ADVANTAGES

´ It has great potential for generating information about

differential sources of effect on the dependent variable,

because all four groups are studied at the same time, both

the effects of events occurring between time 1 and time 2

and the maturation of subjects are controlled.

´ One can examine the score of control groups 2 for a

measure of maturation without the influence of treatment.

´ The invigilator also can compare the different in the groups.

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AFTER / POST TEST ONLY CONTROL GROUP

DESIGN

´ Experimental group


Post test

´ Control group

Post test

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AFTER / POST TEST ONLY CONTROL GROUP

DESIGN

´ This design, which is sometimes called after only

control group design.

´ This is composed on two randomly assignedgroups, but neither of which is pretested or

premeasured in the before period of time.

´ The independent variable introduced intoexperimental group and withheld from the control

group.

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ADVANTAGE

´ This design can be useful in situation where

it is not possible to pretest the subjects or

pretest is non essential

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PRE- EXPERIMENTAL DESIGN

´ It is one type of the experimental design

´ It have three subdivisions. They are

« One short case study or single case study

« One group pretest ² posttest design

« The static group comparison design

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ONE SHORT CASE STUDY OR SINGLE CASE STUDY

Experimental treatment

´ Cause change

´ In single case study, that studies at once, following

a treatment or an agent presumed to cause

change.

´

Because the study design has a total absence of control, it is considered to be little value as an

experiment.

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ONE GROUP PRETEST ± POSTTEST DESIGN

´

Experimental treatment

Pre test post test

´ Here only one group is observed before and after the

independent variable is introduced.

´ Loss of the control group decreases the usefulness of the

study but may be necessary in cases where it is not

possible or feasible to have control groups.

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THE STATIC GROUP COMPARISON DESIGN

´ The static group that has experienced theindependent variable is compared with one

that has not.

´ Here the experimental group received theindependent variable, but control group did

not receive the independent variable.

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QUASI EXPERIMENTAL DESIGN

´ It is one which full experimental control, usuallyrandomization is not possible.

´ It has three subdivisions. They are

Non equivalent control group design or the four celled design

without use of randomization

The time series quasi experimental design

The multiple time series design

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Non equivalent control group design or the four celled design without use of

randomization

´ Experimental group ( not randomly selected)


Pre test Post test

´ Control group ( not randomly selected)

Pre test Post test

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TIME SERIES EXPERIMENTAL DESIGN

´ experimental treatment

´ Pre test 1 2 3 4 5 6 6 5 4 3 2

post test 1

´ The time series experiment design, a single group

experiment comprises of series of observation in the before

time period to establish a baseline. The experimental

variable is then introduced, followed by another series of observation to examine the effect of the independent

variable.

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The multiple time series design

´ Experimental group

experimental matter

´ Pre test 1 2 3 4 5 6 6 5 4 3 2

post test 1

´ Control group

Pre test 1 2 3 4 5 6 6 5 4 3 2post test 1

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NON-EXPERIMENTAL

RESEARCH DESIGNS

´ This type of design is other wise called as

weakest design.

´ Need not obey any principles

´ It have so many subdivisions

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REASONS FOR UNDERTAKING NON

EXPERIMENTAL STUDIES

´ Number of human characteristics/ independentvariables are not subject to experimentalmanipulation or randomization

´ Some variables cannot ethically be manipulated

´ For some research, it is not practical to conduct atrue experiment/manipulate variables

´ For some situations, it is more realistic to explorephenomena in more natural manner

´ Nonexperimental research is often needed toscope out the experimental one

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CLASSIFICATION OF

NON EXPERIMENTAL DESIGNS

´ Descriptive/exploratory survey studies

´ Interrelationship/difference

«

Correlational studies« Ex post facto studies

« Prediction studies

«Developmental studies

²Cross-sectional & longitudinal studies

²Retrospective & prospective studies

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DESCRIPTIVE/EXPLORATORY

SURVEY

´ Broadest category

´ Detailed observations, descriptions &documentation of existing variables

´ Little is known about the phenomenon´ Justifies, assesses current conditions/practice

´ Variables of interest: opinions, attitudes or facts

´ Determines differences between variables

´ Data collected by questionnaire or interview´ Researchers only relate one variable to another,

no attempt to determine causation

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EXPLORATORY SURVEY RESEARCH

´ Designed to obtain information about

« prevalence

« distribution

«

interrelations of variables within a population´ Census vs. sample surveys

´ Self-reporting

´ Flexibility and broadness

´ Superficiality ² extensive vs. intensive analysis

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TWO ASPECTS ABOUT SURVEYS

Survey Content

´ Direct questioning

´ Answering how,

what,and to what extentquestions

´ Usually focus on whatwas done and what

people plan to do in thefuture

Survey Administration

´ Different data collection

methods

« Personal interviews

« Telephone interviews

« Self-administered

questionnaires (SAQs)

« Mixed-mode strategy

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DESCRIPTIVE RESEARCH

´ Purpose is to

« observe, describe, & document aspects of a situation as itnaturally occurs

« serve as a starting point for hypothesis generation or theorydevelopment

´ Types:

« Descriptive Correlational Studies

« Univariate Descriptive Studies

² Prevalence Studies

² Incidence Studies

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DESCRIPTIVE CORRELATIONAL

STUDIES

´ Describes the relationship among variables

rather than infer cause-and-effect relationships

´ Are usually cross-sectional

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UNIVARIATE DESCRIPTIVE STUDIES

´ Could focus on one or more variables

´ Undertaken to describe the frequency of occurrence of a behavior or condition or each

variable rather than relationships between oramong them

´ Types:

« Prevalence Studies

« Incidence Studies

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PREVALENCE STUDIES

´ Done to determine the prevalence rate of somecondition at a specific point in time

´ Data is obtained from the population at risk for

the condition ² cross sectional design

Prevalence Rate (PR) = # cases with condition X K

# in population at risk

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INCIDENCE STUDIES

´ Used to measure the frequency of developing new cases

´ Need longitudinal designs

Incidence

Rate (

IR)=

# new cases with condition over given period X K

# at risk of becoming a new case

´ R

elativeR

isk: an estimate of risk of ´casenessµ in onegroup vs. another; contribution of risk factors

« E.g. males vs females for acquiring depression

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DESCRIPTIVE/EXPLORATORY SURVEY

(CONT¶D)

´ Advantage:

« large amount of information can be

obtained from a large population in an

economical manner which is ´surprisinglyµ accurate´ Disadvantages

« Info tends to be superficial as breadth is emphasized

« Expertise in: sampling techniques, questionnaireconstruction, interviewing and data analysis to produce a

reliable and valid study.

« Time-consuming & sometimes costly

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INTERRELATIONSHIP/DIFFERENCE

STUDIES:

CORRELATIONAL STUDIES´ Examines if variables covary

´ Quantifies the strength or relationship between the variables (not cause &effect)

´ +ve or ²ve direction relationship determined

´ Advantages:

« Increased flexibility when investigating complex relationships among variables« Efficient and effective method of collecting a large amount of data

« Potential for practical application in clinical settings

« Potential foundation for future, experimental studies

« Framework for exploring relationships that are not manipulated.

´ Disadvantages:

« Unable to manipulate variable of interest« No randomization in sampling

« Generalizability decreased as dealing with preexisting groups

« Unable to determine a causal relationship because of the lack of manipulation,control and randomization.

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STUDIES:

EX POST FACTO STUDIES´ Literally means ¶from after the fact·´ Also known as causal-comparative studies or comparative

studies´ Explores differences/relationships between variables (similar

to quasi-experimental designs)

´ Advantages:« Allows for establishment of a differential effect« Similar to correlational designs« Offers a higher level of control

´ Disadvantages:« Lack of control on variables« Unable to draw causal linkage« Problem of alternative hypothesis

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STUDIES:

DEVELOPMENTAL STUDIES´ Not only concerned with existing status &interrelationship of phenomena but also withchanges from elapsed time.

´ Cross sectional (one/more time points, perhapsdifferent groups) vs Longitudinal (several timepoints with same group over extended period)

´ Retrospective (dependent variable has alreadybeen affected by independent variable, link

present events to past events) vs Prospective (linkpresent events to presumed future effect, lesscommon, considered stronger design)

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OTHERS

Natural Experiments: study of a groupexposed to natural or other phenomenon

that have health or other consequences,

compared with a nonexposed group; peopleare affected at random

Path Analytic Studies: using a technique called

path analysis, nonexperimental data is

tested against a hypothesized causal

inference

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EPIDEMIOLOGIC RESEARCH

DESIGNS

´ Cohort studies: trend study in which specificsubpopulations (eg age specific) are examined over timefor generational differences

« prospective & retrospective

´ Case-control study: comparison of cases/subjects (withspecific condition), with controls (without condition); onlydifference should be exposure to presumed cause

´ Cross-sectional design: phenomena under study are

captured during one period of data collection; one point intime

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