T

TYPES OF RESEARCH DESIGN

PRESENTED BYMD AZAM ZIA

(IBT)1/42

Definitions of Research“Systematic investigation towards increasing the sum of knowledge”

(Chambers 20th Century Dictionary)

“An endeavour to discover new or collate old facts etc.by the scientific study of a subject or by a course of critical investigation.”

(The Concise Oxford Dictionary)

2/42

• A research design – 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.”

• A good clinical study starts with – a good question based on good hypothesis that is based on

good and comprehensive review of the available evidence from pre-clinical and clinical data

• Type of design depends on the question to be answered

3/42

RESEARCH DESIGN

RESEARCH DESIGN refers to the plan, structure, and strategy of research--the blueprint that will guide the research process.

4

Developing ResearchHypotheses

Intriguing Observation,Intellectual Curiosity

Defining ResearchProblem & Objectives

Testing Hypo.:Data Analysis &Interpretation

Sampling Design

Refinement of theory(Inductive Reasoning)

Data Coding,And

Editing

Developing OperationalDefinitions for

Research Variables

Building the Theoretical Framework and the

Research Model

Data Collection

More Careful Studyingof the Phenomenon

THE PROCESS OF

EMPIRICAL RESEARCH

• The designing decisions happen to be in respect of:– (i) What is the study about?– (ii) Why is the study being made?– (iii) Where will the study be carried out?– (iv) What type of data is required?– (v) Where can the required data be found?– (vi) What periods of time will the study include?– (vii) What will be the sample design?– (viii) What techniques of data collection will be used?– (ix) How will the data be analyzed?– (x) In what style will the report be prepared?

5/42

• The important features of a research design(i) a plan

• specifies the sources & types of information relevant to the research problem

(ii) a strategy • which approach will be used for gathering and

analyzing the data.

(iii) the time and cost budgets• most studies are done under these two constraints

6/42

7

cont…

CONCLUSION VALIDITY refers to the extent of researcher’s ability to draw accurate conclusions from the research. That is, the degree of a study’s:

a) Internal Validity—correctness of conclusions regarding the relationships among variables examined • Whether the research findings accurately reflect how the research variables

are really connected to each other.

b) External Validity –Generalizability of the findings to the intended/appropriate population/setting• Whether appropriate subjects were selected for conducting the study

RESEARCH DESIGNRESEARCH DESIGN:: The The blueprint/roadmapblueprint/roadmap that will guide the that will guide the research. research. The test for the The test for the quality of a study’s research design quality of a study’s research design is theis the study’s study’s conclusion validityconclusion validity..

8

Cont..

• Variance of the INDEPENDENT & DEPENDENT variables (Systematic Variance)

• Variability of potential NUISANCE/EXTRANEOUS/ CONFOUNDING variables (Confounding Variance)

• Variance attributable to ERROR IN MEASUREMENT (Error

Variance). How?

How do you achieveHow do you achieve internal and external validity internal and external validity (i.e., conclusion validity)?(i.e., conclusion validity)? By effectively By effectively controlling 3 types of controlling 3 types of variancesvariances::

9

Effective Research Design

– MAXimize Systematic Variance– MINimize Error Variance– CONtrol Variance of Nuisance/Extraneous/

Exogenous/Confounding variables

Guiding principleGuiding principle for effective control of variances (and, for effective control of variances (and, thus, effective research design) is: thus, effective research design) is:

The The MAXMINCONMAXMINCON Principle Principle

10

Effective Research Design

Adequate (full range of) variability in values of research variables,

Precise and accurate measurement, Identifying and controlling the effects of confounding variables,

and Appropriate subject selection

RECAP:RECAP:Effective research design is a function of ?Effective research design is a function of ?

DIFFERENT RESEARCH DESIGNS

1. Exploratory research studies 2. Descriptive and diagnostic research

studies 3. Hypothesis-testing research studies

11/42

1. Exploratory research studies It is also termed as formulative research studies The main purpose

• formulating a problem for more precise investigation • of developing the working hypotheses from an

operational point of view• The major emphasis is on the discovery of ideas and

insights• Generally, three methods in the context of research

design for such studies

(a) the survey of concerning literature; (b) the experience survey; and(c) the analysis of ‘insight-stimulating’ examples.

12/42

• The survey of concerning literature – to be the most simple and fruitful method of formulating

precisely the research problem or developing hypothesis. • Hypotheses stated by earlier workers may be reviewed

and their usefulness be evaluated as a basis for further research.

• It may also be considered whether the already stated hypotheses suggest new hypothesis.

• Experience survey– To obtain insight into the relationships between variables and

new ideas relating to the research problem.

13/42

• 3. Hypothesis-testing research studies • known as experimental studies or design of

experiments• Tests the hypotheses of causal relationships

between variables • Usually experiments meet this requirement Three basic principles of experimentaldesigns

• (1) the Principle of Replication; • (2) the Principle of Randomization; • (3) Principle of Local Control.

14/42

Study Designs

Descriptive Analytic Experimental

correlational

case report/case series

cross-sectional

case control

cohort

clinical trial

community trial

Types of research design A. Experimental research designs

(a) Informal experimental designs• (i) Before-and-after without control design.• (ii) After-only with control design.• (iii) Before-and-after with control design.

(b) Formal experimental designs• (i) randomized controlled design (C.R. Design) a. Clinical trails , b. Filled trails , c. Community trails • (ii)Randomized duplicate design• (iii) Randomized block design (R.B. Design).• (iv) Latin square design (L.S. Design).• (v) Factorial designs

16/42

B. Observational research designI. CROSS - SECTIONAL designII. COHORT designIII. CASE CONTROL designIV. CASE SERIES/CASE REPORTS

C. Diagnostic research designs Screening design

D. Exploratory research designsI. Survey concerning literatureII. Insight stimulating studiesIII.Experience surveys

17

BASIC DESIGNS

• Experimental Designs:– True Experimental Studies– Pre-experimental Studies– Quasi-Experimental Studies

• Non-Experimental Designs:– Expost Facto/Correlational Studies

18

SPECIFIC TYPES OF RESEARCH DESIGN

BASIC RESEARCH DESIGNS:

19/42

Experimental research designs

Before-and-after without control design– A single test group or area is selected, and the

dependent variable is measured – The treatment is then introduced and then the

dependent variable is measured again – The effect of the treatment

• the level of the phenomenon after the treatment - the level of the phenomenon before the treatment

20/42

The design can be represented thus:

21/42

After-only with control design– Two groups or areas (test area and control area) are selected and

the treatment is introduced into the test area only

22/42

Before-and-after with control design

23/42

Completely randomized design (C.R. design) Two-group simple randomized design

24/42

Randomized duplicate design

25/42

26/42

Randomized block design (R.B. design)

Latin square design (L.S. design) – An experimental design very frequently used in

agricultural research

27/42

Factorial designs– where the effects of varying more than one factor

are to be determined. – important in several economic and social

phenomena– Factorial designs can be of two types:

• (i) simple factorial designs • (ii) complex factorial designs

28/42

• Illustration 1: (2 × 2 simple factorial design). A 2 × 2 simple factorial design can graphically be depicted as follows:

29/42

30/42

31/42

• Factorial designs are used mainly because of the two advantages (i) provide equivalent accuracy

determine the main effects of two (in simple factorial design) or more (in case of complex factorial design) factors (or variables) in one single experiment.

(ii) permit various other comparisons of interest

32/42

33

CLINICAL TRIALS

34

Clinical Trials – Drug Development

BasicResearch

NovelCompounds

SafetyTesting

Drug Licensing& Release

In-VitroScreeningIsolated cells

& tissues

In-VivoScreening In A

nimals

Clinical Trials I - IIIIn Humans

35

Clinical Trials-PhasesClinical Trials-Phases

Phase I - Does it hurt the Patient?Phase I - Does it hurt the Patient? Usually in normal volunteers, small groups for safety testingUsually in normal volunteers, small groups for safety testing

Phase II - Does it help the Patient?Phase II - Does it help the Patient? On patients to confirm the effectiveness of the drugOn patients to confirm the effectiveness of the drug

Phase III - Is it any better?Phase III - Is it any better? Large groups of patients for statistical confirmation of effect Large groups of patients for statistical confirmation of effect

and incidence of side-effectsand incidence of side-effects Phase IV - Does it work in the community?Phase IV - Does it work in the community?

Post marketing studies. Fine tuning and new rare findings Post marketing studies. Fine tuning and new rare findings from a very large populationfrom a very large population

36

Clinical Trial: Study DesignClinical Trial: Study Design

UncontrolledUncontrolled ControlledControlled

Before/after (cross-over)Before/after (cross-over) HistoricalHistorical Concurrent, not randomizedConcurrent, not randomized RandomizedRandomized

37

Advantages of Randomized Control Clinical Trial

1. Randomization "tends" to produce comparable groups

2. Assure causal relationship

3. Randomization produces valid statistical tests

38

Disadvantages of Randomized Control Clinical Trial

1. Generalizable Results?– Participants studied may not represent general

study population.

2. Recruitment– Hard

3. Acceptability of Randomization Process– Some physicians will refuse– Some participants will refuse

4. Administrative Complexity

• Observational research design

39/42

Cross - Sectional Study (1)• Exposure and disease measured once, i.e. at the same

point in time

40

present futurepast

n

exposed ?diseased ?

Cross - Sectional Study (2)

• Random sample from population– i.e. results reflect reference population

• Estimates the frequencies of both exposure and outcome in the population

• Measuring both exposure and outcome at one point in time

• Typically a survey

41

Cross - Sectional Study (3)• Can study several exposure factors and outcomes

simultaneously • Determines disease prevalence• Helpful in public health administration & planning• Quick• Low cost (e.g. mail survey)• Limitation:

– Does not determine causal relationship– Not appropriate if either exposure or outcome is rare

42

Cross-Sectional: Pediatrician-to-Child Ratio

43

Greg et al. (2001) Pediatrics.107(2):e18

05

10152025303540

Pedi

atri

cian

s pe

r 10

00 C

hild

ren

Rural Urban

1981198619911996

Cohort Studies

44

Cohort studies

• Follow-up studies; subjects selected on presence or absence of exposure & absence of disease at one point in time. Disease is then assessed for all subjects at another point in time.

• Typically prospective but can be retrospective, depending on temporal relationship between study initiation & occurrence of disease.

45

Cohort Study (1)

• More clearly established temporal sequence between exposure & disease

• Allows direct measurement of incidence• Examines multiple effects of a single exposure

(nurses’ health study, OC and breast, ovarioan cancers)

46

Cohort studies (2)

• Limitations: – time consuming and expensive – loss to follow-up & unavailability of data – potential confounding factors – inefficient for rare diseases

47

Prospective Cohort Study

48

without outcome

Cohort

with outcome

with outcome

withoutoutcome

Exposed

Unexposed

TimeOnsetof study Direction of inquiry

Q: What will happen?

Case-Control Studies

49

Case-Control Study (1)

• Retrospective– Can use hospital or health register data

• First identify cases• Then identify suitable controls

– Hardest part: who is suitable ??• Then inquire or retrieve previous exposure

– By interview– By databases (e.g. hospital, health insurance)

50

Case-Control Study (2)

• Good for rare disease (e.g. cancer)• Can study many risk factors at the same

time• Usually low cost• Confounding likely

51

Case-Control Study Design

52

Cases

Controls

Exposed

Unexposed

Exposed

Unexposed

TimeDatacollection

Direction of inquiryQ: What happened?

53/42

54

Questions or Comments

?