21582250 Research Methodology Ppt
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Transcript of 21582250 Research Methodology Ppt
Research methodology
contentsIntroduction to researchDefinitions
ResearchThesisDissertation
Why to do a researchCategories of researchResearch methods & research methodologyProcedural steps in researchResearch strategy epidemiologic studiesEthics in research
Introduction
Investigation using scientific procedures, by searching again and again to find out the truth
Research is the continual search for truth using the scientific method. It is the pursuit of the truth with the help of study, investigation, observation, comparison and/or experimentation.
definitions
Research (WHO Health research methodology, 1992, a guide for training in research methods):
Research is a quest for knowledge through diligent search or
investigation or experimentation aimed at the discovery and
interpretation of new knowledge. Scientific method is a
systematic body of procedures and techniques applied in
carrying out investigation or experimentation targeted at
obtaining new knowledge. Here research and scientific
methods may be considered a course of critical enquiry leading
to discovery of facts or information which increases our
understanding of human health and disease.
Thesis
(according to Oxford English dictionary)
A proposition laid down as a theme to be
discussed and proved. A discussion to
maintain and prove a thesis especially
written or delivered by a candidate for
university degree- Ph.D
Dissertation:
• Dissertation means “to discuss”.
• It is an academic activity laid down by the university for the
partial fulfillment of MDS degree.
• It is an exercise to train a PG student to plan, execute, evaluate,
write and report a scientific project.
• It is an in-depth study of a particular topic which contributes new
information and knowledge in the field
• A formal, often lengthy treatise (a book or writing of some
particular subject, one containing a methodical discussion or
exposition of principles of subject) or discourse, especially one
written by a candidate for a master’s degree.
It is a pre-requisite or academic activity for acquiring a masters degree or doctorial.
To find out the truth which is hidden and which has not been discovered yet.
To contribute new knowledge to the existing one as the scientific knowledge develops in increments.
As a profession to conduct research in various aspects.
To solve an existing health problem.
For thrill and enjoyment of discovering a new fact.
Categories of research
Empirical research and theoretical research
Basic research and Applied research Empirical
Observational research
Experimental research
Basic or pure research
It is usually considered to involve the search for knowledge without a defined goal of utility or specific purpose.
Eg. The microbiologist, whose expertise is the identification of pathogenic micro organisms may conduct research in-vitro, in a laboratory on bacterial reproduction, growth and endotoxin production without any direct application to clinical dentistry. Probably, the researcher is interested in monitoring endotoxins produced over the life cycle of bacteria to determine a pathogenecity.
Applied research
It is problem oriented and is directed towards a defined and purposeful end.
Eg. An oral health researcher investigating the relationship between periodontal disease and myocardial infarction may use the findings of the microbiologist as a theoretical framework to test the relationship between bacterial endotoxins, periodontal disease and myocardial infarction in animal and then in human subjects
Research methods
methods/ techniques that are used for conducting research are termed as research methods or research techniques.
They fall into 3 groups
1. Those concerned with collection of data
2. Those statistical techniques which are used for establishing relationship between the data and the unknown
3. Those methods which are used to evaluate the accuracy of the results obtained.
identify problemLiteratur
e reviewPlan research
design
Determining sample
size
Write protocol
Ethical committee approval
Pilot study and main
study
Presentation &analysis of results
Hypothesis testing
Generalisation interpretation
Report writing
publication
Pr
oced
ural
ste
ps in
rese
arch
Selection of problem for investigation-further exploration Inexperienced-seek opinion –senior Constructing –essential starting point
Review literature Modern electronic research Abstract collection held on CD-ROMS-enables –key words Medline and psyclit database Role of systemic review grown recently-cochrane
collaboration-reviews from volunteer researchers internationally adds them to a bank,which is open for inspection by interesting parties.
Specifying study design
Selection of measures: many measure ,assessments Eg:self report rating scales for dental
anxiety,observations,interviews,stand questionnaires simple rating scale can be given a no.1-strongly agree 2-agree 3-undecided 4-disagree 5-strongly disgree May not exist for the study ,this may necessiate the
development of new scale. should possess Reliability and validity
Selection of sample: Sampling techniques-inorder to provide information ,can be generalised
to cover the whole population.
Writing a protocol: aims & objectives,method,materials,sample ,procedure
Ethical approval Pilot work Main study Analysis of results Report writing publication
Research strategies
Selection of a research strategy is the core of a research design and is probably the single most Important decision the investigator has to make, i.e. whether to undertake a descriptive, an analytical or an experimental study.
Classification of Epidemiologic studies
Observational studies
Descriptive studiesSurveys
(questionnaire or others)
Case studies
Correlational studies
Analytical studies
Ecological or correlational
studies
Cross-sectional or prevalence
studies
Case-control or case-
reference studies
Cohort or follow-up studies
Experimental or intervention studies
Randomised
controlled trials or clinical trials
Field trials or
community
intervention studies
Community trials
Decscriptive study
Concerned with observing the distribution of disease or health related characteristics in human population
Eg. Surveys. Defining population:denominator Defining the disease:operational definition. Describing disease-time,place and personTime: Short term fluctuation:
1. Common source epidemics-single,continuous2. Propagated epidemics-person to person transmission of
infectious agent---epidemics of hepatitis A and poliomyelitis3. Slow or modern epidemics
Periodic fluctuations: Seasonal –communicable diseases like
measles,varicella,malariaEg:upper Resp tract infections inc during winter and GI inf in
summer Cyclic trends-measles-incidence every 2-3 yrs Influenza occurs at intervals of 7-10 yrsLong term fluctuation Changes occur over long period of time,change in frequency
encompassing sev decadesEg:CHD,diabetes,lung cancer shows upward trend in 50 decades
and TB, typhoid downward
Place distribution:Interanational-National-endemic disease like goitre,flourosisRural-urban-lung cancer,cardiovascular accidents-urbanLocal-spot maps (john snow –on epidemic of cholera)and shaded
maps -study
Person distribution:age sex Measurement of disease :morbidity and mortality indicators
Expressed in terms of incidence and prevalence Comparing with known indices:comparision b/n different
population and subgroups of same populn-clue to etiology Formulation of hypothesis:relating to disease etiology specify-population,sp cause ,expected outcome,dose-
response r/n,time-resp r/n.Eg:smoking of 30-40 cigarettes/day causes lung cancer in
10% of smokers after 20 yrs of exposure.Uses:1. magnitude and type of disease in community2. Clues to etiology3. contributes to research
surveys
Surveys are methods of scientific or systematic collection of data, compiling, presenting in order (useful manner), analysing and evaluating them
The focus of attention must be on the followinga) Formulating the objective of the study-obj describing
what is to be measured,resources
b) Designing the method of data collection eg. Questionnaires, interviewing, examination of records or observations
c) Selecting the sample
Conducting examination:1. Obtaining approval from authorities2. Budgeting3. Scheduling4. Emergency care and refferal5. (diagnostic method)Validity and reliabilty of the data
Classification of study types-ADA(1970)typeI: complete examinationtypeII: limited examinationType III: inspectionType IV:screening procedures:tongue depressor
d) Analysing the datae)Drawing the conclusionf) Publishing the reports
Case study: it is an intensive investigation of a person, a family, a group, a social institution or an entire community in a natural setting
Correlational study: it is a descriptive research technique utilized to identify consistent relationship among variables
Analytical study
Second major typeSubject of interest –individual with in populationObject –not to formulate but test hypothesis
Can determine:1.Statistical association between disease and
suspected factors2.If exists--strength
Case control studies Design of a case-control study
Time
Direction of enquiry
Exposed
Not Exposed
Cases
Not Exposed
Exposed
Controls
Population
Defining the cases and controls: Case: you have to decide a case before the start
of the study. The case has to fit in to two criteria.
1. Diagnostic criteria.
2. Eligibility criteria. only newly diagnosed cases within a specified
period of time than old cases
Selection of cases
The criteria for inclusion in the study must be clearly specified.
Sources of cases:
▪ Hospitals
▪ General population
Controls they must be as similar to the cases as possible, except for
the absence of the disease,which is under study.
Selection of controls Crucial step in case-control studies
Controls must be
▪ Be similar to the cases except for the absence of the disease under study
▪ Equal ratio
Sources of controls Hospitals:diff illness
Relatives
Neighborhood controls
General population
Matching
Definition:
the process by which we select controls in such a way that they are similar to cases with regard to certain pertinent selected variables, which are known to influence the out come of disease and which, if not adequately matched for comparability, could distort or confound the results.
Example: age.
Confounding factor One which is associated both with exposure and disease; and is
distributed unequally in study and control groups Although associated with ‘exposure’ under investigation, it itself
is a risk factor for the disease
Measurement of exposure Exposure can be measured by
Interviews Questionnaires By studying past records Examinations
Bias/ systematic error should be avoided while measuring the exposure
Analysis Involves two steps1. Exposure rates among cases and controls2. Estimation of disease risk associated with
exposure (odds ratio)
1. Exposure rates
cases controls
Smokers
33(a)
55(b)
non Smokers
2( c )
27(d)
Total 35(a+c)
82(b+d)
Exposure rate among cases= (a/a+c)100 = (33/35) 100 = 94.2 %
Exposure rate among controls= (b/b+d)100 = (55/82) 100 = 67 %
A case control study of smoking and lung cancer
2.Estimation of risk
Cases Controls
Smokers 33(a)
55(b)
Non smokers
2( c )
27(d)
Total 35(a+c)
82(b+d)
= a/(a+b) / c/(c+d)Relative risk =
Incidence among non exposed Incidence among exposed
Relative risk (RR) or Risk ratio
Odds ratio (cross product ratio)
It is a key parameter in the analysis of case control studies
A measure of the strength of the association between risk factor and outcome
Derivation of odds ratio is based on 3 assumptions
Disease under investigation is a rare one Cases are representative of those with disease Controls are representative of those without
disease
Odds ratio = ad/bc = 33 X27/ 55X2 = 8.1
Smokers have a risk of having lung cancer 8.1 times that of non smokers
cases controls
smokers 33(a)
55(b)
Non smokers 2( c )
27(d)
total 35(a+c)
82(b+d)
Bias in case control study1. Bias due to confounding2. Memory bias3. Selection bias4. Berksonians bias:different rates of admission to
hosp for people with diff disease5. Interviewer’s bias
advantages of …
Relatively easy to carry out Rapid and inexpensive (compared with cohort studies) Require comparatively few subjects suitable to investigate rare diseases or diseases
about which little is known. No risk to subjects Allows the study of several different aetiological factors (e.g.,
smoking, physical activity and personality characteristics in
myocardial infarction) No attrition problems, because case control studies do not
require follow-up of individuals into the future Ethical problems minimal
Disadvantages of … High chances for bias
Validation of information obtained is difficult or sometimes impossible
Selection of an appropriate control group may be difficult
We cannot measure incidence, and can only estimate the odds ratio but not relative risk
Not suited to the evaluation of therapy or prophylaxis of a disease
Another major concern is the representativeness of cases and controls
Cohort studies
Usually undertaken to obtain additional evidence to refute or support the existence of an association
between suspected cause and diseaseOther names
Incidence study
Forward looking study
Longitudinal study
Prospective study
distinguishing Features of …
Cohorts are identified prior to the appearance of
the disease under investigation
Study groups are observed over a period of time
to determine the frequency of disease
The study proceeds from cause to effect
Cohort is defined as a group of people who share
a common characteristic or experience within a
defined time period
Eg, birth cohort,age cohorts, occupational
cohorts, exposure to a drug cohorts, marriage
cohort etc.
The comparison group may be…
the general population from which the cohort is
drawn
Indications for …
When there is a good evidence of an
association between exposure and disease
When the exposure is rare but the incidence
of disease is high among exposed
When the attrition can be minimised
When ample funds are available
Design of a cohort study
Population free of
condition
Screening to exclude those with the condition
SAMPLE
With the characteristic
Without the characteristic
Time
DevelopDisease
Do not develop disease
DevelopDisease
Do not develop disease
Time
Direction of enquiry
a
b
c
d
Considerations for selecting cohorts
Cohorts must be free from the disease under study
both the groups should be equally susceptible to disease under study
Both the groups should be comparable in respect of all possible variables, except the assumed risk factors
Diagnostic and eligibility criteria of the disease must be defined beforehand.
Inclusion and exclusion criteria should be clearly stated before the commencement
Steps in …
Selection of study subjects
Obtaining data on exposure
Selection of comparison groups
Follow up
Analysis
Selection of study subjects
Cohorts can be selected from
General population
Special groups
▪ Select groups (eg. Doctors, lawyers, teachers, etc.)
▪ Exposure groups
Obtaining data on exposure
Information can be obtained from
Cohorts
Review of records
Medical examination or special tests
Environmental surveys
Information about exposure should facilitate
classification of cohort members
According to whether or not they were exposed
According to the degree of exposure
Selection of comparison groups
Internal comparisons: no outside comparision group is required
External comparisons: when degree of exposure is not available,ext
cohort .eg:smokers and non smokers,radiologists and opthamologists.
Comparison with general population:mortality experience of exposure group is
compared with mortality experience of general populationin same geographic area
Follow up
Periodic medical examination of each member
Reviewing physician and hospital records
Routine surveillence of morbidity and mortality
records
Mailed questionnaires, telephone interviews,
periodic home visits
Analysis
Data is analysed interms of
i. Incidence rates of outcome among exposed and non-exposed
ii. Estimation of risk
▪ Relative risk
▪ Attributable risk
Incidence rates
Incidence can be
measured directly
Incidence rate among
smokers = 70/7000 =
10 per thousand
Incidence rate among
non-smokers= 3/3000 =
1 per 1000
P < 0.001
Cigarette smoking
Lung canc
er
No lung canc
er
Total
Yes 70a
6930b
7000a+b
No 3c
2997d
3000c+d
Relative risk Relative risThe ratio of
incidence among exposed and incidence among non-exposed
Also called ‘risk ratio’
RR=
RR is the direct measure of strength of association between suspected cause and effect
Incidence among exposedIncidence among non-exposed
=
10/1 = 10
Cigarette smoking
Lung canc
er
No lung canc
er
Total
Yes 70a
6930b
7000a+b
No 3c
2997d
3000c+d
RR-i= no assossiationRR > 1= positive assossiation
Attributable risk
The difference in incidence rates between exposed and non-exposed groups
Also called risk difference
of
lung cancer was due to their smoking It indicates to what extent disease can be
attributed to the exposure Suggests the amount of disease that might be
eliminated if the factor could be controlled
Incident rate among exposed – incidence rate among non-exposedIncident rate among exposed
X 100
(10-1/10) X 100 = 90%
Relative risk X Attributable risk
Relative risk Etiological enquiries Larger the RR,
stronger the association between risk factor and outcome
Does not reflect the potential public health importance
Attributable risk Gives a better idea of
the impact of a successful intervention might have in reducing the problem
Advantages of cohort studies
Allow the possibility of measuring directly
the relative risk of developing the condition for those
who have the characteristic, compared to those who
do not
Allows for a conclusion of cause-effect relationship
Because the presence or absence of the risk factor is
recorded before the disease occurs, there is no chance
of bias
Cohort studies are capable of identifying
other diseases that may be related to the
same risk factor. Unlike case-control studies, cohort studies
provide the
possibility of estimating attributable risks,
thus indicating the absolute magnitude of
disease attributable to the risk factor.
Disadvantages of cohort studies Not always feasible. Relatively inefficient for studying rare conditions. They are very costly in time, personnel, space and patient
follow-up. Sample sizes required for cohort studies are extremely large,
especially for infrequent conditions; it is usually difficult to find
and manage samples of this size. The most serious problem is that of attrition, which can affect the
validity of the conclusion, if it renders the samples less
representative, or if the people who become unavailable are
different from those actually followed up. The higher the
proportion lost (say beyond 10-15%) the more serious the
potential bias.
There may also be attrition among investigators who maylose interest, leave for another job, or become involvedin another project.
Over a long period, many changes may occur in theenvironment, among individuals or in the type ofintervention, and these may confuse the issue ofassociation and attributable risk.
Case control study cohort study
Proceeds from effect to cause Starts with the disease Tests whether the suspected
exposure occurs more frequentlyin those with the disease thanamong those without thedisease.
Involves fewer number ofsubjects
Yields relatively quick results Suitable for the study of rare
diseases Generally yields only estimate
of RR (odds ratio) Cannot yield information about
diseases other than thatselected for study
Relatively inexpensive
Proceeds from "cause to effect". Starts with people exposed to risk
factor or suspected cause. Tests whether disease occurs more
frequently in those exposed, than in those not similarly exposed.
Involves larger number of subjects
Long follow-up period often needed, involving delayed results.
Inappropriate when the disease or exposure under investigation is rare.
Yields incidence rates, RR as well as AR.
Can yield information about more than one disease outcome.
Expensive.
Experimental studies
Study of epidemics among colonies of experimental animals such as rats and mice .
AIMS To provide scientific proofs of etiological factors To provide a method of measuring the effectiveness and
efficiency of health services has all adv and disadv of cohort study and also
ethics,cost and feasibility Animal studies: important applicationAdvantages1. Bred in lab,and can manipulated easily2. They multiply rapidly Disadvantages:3. Not all human diseases can be reprodeuced4. All conclusions – not applicable
Human studies:To investigate disease etiology and to evaluate the
preventive ,therapeutic measures1747-john lind-scurvy1796-Edward Jennar-cowpox 1. Ethical and logistic considerations,benefits
weighed againsts the risks involved2. Volunteers –made fully aware of the experiment3. WHO (1980)-strict code of practice
Experimental studies
Randomised controlled trials:
Involves some action,intervention or manipulation such as deliberate application or withdrawl of suspected cause.
1. Drawing up a protocal
2. Selecting reference and experimental population
3. Randomization
4. Blinding
5. Manipulation or intervention
6. Follow- up
7. Assessment of outcome
Randomised controlled trials
Non-randomized trials
Select population (Reference or target population)
Select suitable sample (Experimental or study population)
Selection by defined criteria
Potential participants (Meet selection criteria)
Non-participants(do not meet selection criteria)
Invitation to participate Non-participants(do not give consent)
Participants
Randomization & double blinding
Experimental group Manipulation,Follow up
& Assessment
Control group
DEsiGN oF
aN
RCT-DB
Positive results: benefit of exp measure----reduced incidence or severity of disease or other appropriate outcomes of study.
Negative results: severity and frequency of side effects and complications ,if any death
Blinding: Randomization cannot guard against these sorts of bias nor the
size of the sample.the technique known as blinding is adopted which can be done in
Single blind trial: here the participant is not aware whether he belongs to study
group or control group. Double blind trial; Here neither the doctor nor the participant is aware of the group
allocation and the treatment received.Triple blind trial: Here the participant,the investigator and the analyzer are all
‘’blind’’.
Ethics in research
First important code of ethics was the NURENBURG CODE of 1947. “No research could proceed in human subjects without voluntary consent.”
Declaration of Helsinki code of ethics on principles of ethical behaviour was established in HELSINKI-I in 1975.
The term “clinical research” to “biomedical research” was revised in HELSINKI- II in 1975
institutional ethics committee or institutional review board
Institutions undertaking clinical trials have to constitute an Institutional Ethics Committee (IEC) or Institutional Review Board (IRB).
It is mandatory that each dissertation research proposal (synopsis) involving humans (irrespective of type of study, including questionnaire based surveys) or animals should be accompanied by a clearance letter from IEC.
ethics and its principles
The science of ideal human character and behavior in situations where distinction must be made between right and wrong, duty must be followed and good inter-personal relations maintained.
When considering the ethical aspect of health research the following principles should also be kept in mind. (Helsinki declaration)
Ethical principles
1. Non-malificence2. Benificience 3. Veracity or truthfulness4. Autonomy5. Justice6. Confidentiality
An application should be submitted to the ethics committee in the following manner 1. Clear research objectives and rationale for
undertaking the investigation in human subjects in the light of existing knowledge.
2. Subject recruitment procedures.
3. Inclusion and exclusion criteria for entry of subjects in the study.
4. Precise description of methodology of the proposed research, including intended dosage of drugs, planned duration of treatment and details of invasive procedures if any.
5. A description of plans to withdraw or withhold standard therapies in the course of research.
6. The plans for statistical analysis of the study.
7. Procedure for seeking and obtaining informed consent with sample of patient information sheet and informed consent forms in English and regional languages.
8. Safety of proposed intervention and any drug or vaccine to be tested, including results of relevant laboratory and animal research.
9. For research carrying more than minimal risk, an account of plans to provide medical therapy for such risk or injury or toxicity due to over dosage should be included.
10. Proposed compensation and reimbursement of incidental expenses.
11. Storage and maintenance of all data collected during the trial.
12. Plans for publication of results- positive or negative- while maintaining the privacy and confidentiality of the study participants.
13. A statement on probable ethical issues and steps taken to tackle the same.
Considerations to be kept in mind while conducting research:
In any research on human beings, each subject must be adequately informed of the aim, methods, anticipated benefits and potential hazards of the study and the discomfort it may entail.
When obtaining informed consent, we should be cautious if the subject has a dependent relationship to us. No pressure or threat should be exercised.
In case of legal incompetence informed consent should be obtained from the legal guardian in accordance with the existing legislation.
Subject should be informed that they are free to abstain or to withdraw from participation at any time
references Behavioural sciences for dentistry. G.Humphris &
M.S.Ling. Churchill Livingstone.2000.
Health research methodology- a guide for training in research methods. WHO 1992
Critical thinking; understanding and evaluating dental research. D.M.Brunette. Quintessence publishing. 1996.
Dentistry, dental practice and community. 5th edition. B.A. Burt & S.A.Eklund. WB Saunders company.
Park’s text book of preventive and social medicine. 19th edition. K.Park. Bhanot publishers. 2007.
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