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INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.india...
RESEARCH
METHODOLOGY
Dr. Murtuza M. Agashiwalawww.indiandentalacademy.com
Contents
• Introduction
• Research - defn. and types, scientific foundation
• Hypothesis – formulation, types
• Steps in c...
Introduction
Why do Research?
- To promote basic knowledge.
- To develop new treatment modalities.
- To inform the public
...
• Research is a quest for knowledge through diligent search
or investigation or experimentation aimed at the discovery
and...
RESEARCH METHODOLOGY
1. Is a way to systematically
solve the research problem
2. It may be understood as a
science of stud...
TYPES OF RESEARCH
All research can be broadly classified into
two types:
1. BASIC Vs APPLIED
2. OBSERVATIONAL Vs EXPERIMEN...
BASIC Vs APPLIED
• Basic research is also called fundamental research.
It is a search for knowledge without a defined goal...
OBSERVATIONAL Vs EXPERIMENTAL
RESEARCH
• There are fundamentally two ways in
which research questions can be
answered:-
• ...
• Qualitative research deals with
subjective aspects which are
qualitative or qualities by nature
which are difficult to q...
CONCEPTUAL VS EMPIRICAL
CONCEPTUAL
Research is that related
to some abstract idea or
theory. It is generally
used by philo...
SCIENTIFIC FOUNDATIONS OF RESEARCH
1) Order
2) Inference & chance
3) Maintenance of probability
4) Hypotheses
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ORDER
Research employs an
organized observation of
entities or events which
are classified or ordered
on the basis of comm...
INFERENCE & CHANCE
Reasoning or inference is the force of advance in
research. There are two distinct approaches in the
de...
MAINTENANCE OF PROBABILITY
Maintaining a very high probability & eliminating the
chance occurrence is critical to ensure t...
Hypothesis is defined as a presumption, supposition
or assumption derived either out of observation or
reflection.
Hypothe...
METHODS OF GENERATING HYPOTHESIS
Mill’s canons of inductive reasoning are frequently
utilized in the forming of hypothesis...
MILL’S CANONS OF INDUCTIVE
REASONING
1.Method of difference:
When the frequency of a disease is
markedly dissimilar under ...
2. Method of agreement:
If a factor’s presence or absence is
common to number of circumstances that are
found to be associ...
3. Method of concomitant variation;
( Dose Response effect)
Eg. Decreasing level of Iodine, with increasing
expression of ...
4. Method of analogy
The distribution and frequency of a disease or
effect may be similar enough to that of some
other dis...
Formulation of hypothesis
• Should specify :
– The population
– Specific cause
– Expected outcome
– Dose response relation...
EXAMPLE OF HYPOTHESIS
• E.g. ‘cigarette smoking causes lung
cancer’ – incomplete
• ‘the smoking of 30-40 cig/day causes
lu...
I.
 Directional hypothesis
 Non directional hypothesis
II.
 Research hypothesis
 Null hypothesis
III.
 Simple hypothe...
1.Directional hypothesis
Is one that specifies not only the existence but the
expected direction of the relationship betwe...
2.Non directional hypothesis
Does not stipulate the direction of the relationship.
A. There is an association between the ...
1.Research hypothesis (substantive or scientific hypotheses):
Are statements of actual expected relationships
between vari...
1.Simple hypothesis:
A hypothesis can predict the relationship
between a single independent variable and
a single dependen...
E) DATA COLLECTION by
1.Mere Observation
2.Intervention followed by observation
PROCEDURAL STEPS IN CONDUCTING RESEARCHPRO...
Sampling
• Sampling is the process or technique of
selecting a sample of appropriate
characteristics and adequate size.
• ...
Sampling
• The total of the elements of the population
under the survey is called “sampling frame”.
• The sample is drawn ...
Advantages of Sampling:
1) Sampling reduces the cost of investigation, the time
required and the number of personnel invol...
Requisites for a Reliable Sample
1) Efficiency - Ability of the sample to yield the desired
information.
2) Representative...
5) Coverage - Adequate coverage of the sample is essential if
it is to remain representative. High rates of refusal,
unava...
Sampling Procedure
Probability
samples
Non-Probability
samples
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Probability samples
Probability samples are those in which it is possible to ascertain the
probability that a unit of the ...
ii) Systematic Sampling-
The first unit is chosen at random and then other
units for the sample are chosen in a systematic...
iv) Cluster Sampling-
It involves choosing groups of units or clusters at
random. All the units in each group, or samples ...
vi) Multiphase Sampling-
It is used to take basic data from a large
sample and details from sub sample. This is
different ...
Non probability sampling
i) Accidental or incidental sampling – people who
have assembled in a common place with a common
...
iii) judgment sampling –
Sample selection is based on the judgment of
the person entrusted with the job
iv) Convenience sa...
• Discrete:- They are called as attributes. They are
qualitative in nature e.g.: Race, Sex, Religion etc.
• Continuous:- T...
Four principal scales :
1.Nominal scale
2.Ordinal scale
3.Interval scale
4.Ratio scale
SCALES OF MEASUREMENT OF DATA
www.i...
1. Nominal scale:- This scale
uses names or tags to
distinguish one measurement
from another. It does not
imply magnitude ...
Ordinal scale:- it is like nominal scale but
there exists an implicit graded order
relationship among the categories.
Eg. ...
• Interval scale:
A numerical unit of measurement is used in this scale.
The difference between any two measurements can b...
Ratio scale
• It is as same as interval
scale in every aspect
except that measurement
begins at a true or
absolute zero.
e...
EPIDEMIOLOGY
EPI = AMONG DEMOS = PEOPLE LOGOS = STUDY
DEFINITION OF EPIDEMIOLOGY
"Epidemiology is the study of the distrib...
Classification of studies
•Descriptive study
•Analytical study
Cross sectional studyCross sectional study
Case control s...
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Design Options
• Directionality
• Timing
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Directionality
• When the exposure variable is observed
relative in time to when the health outcome
is observed.
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Forward Directionality
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Backwards Directionality
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Non-Directionality
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Timing
• Timing concerns whether the health
outcome of interest, and therefore all
study events, has already occurred befo...
Retrospective
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Prospective
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DESCRIPTIVE STUDYDESCRIPTIVE STUDY
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Descriptive study
• Allows…formulation of hypothesis…
• 1st
phase of an investigation
They ask the question
– When…time di...
• Procedure in descriptive study
– Defining population to be studied
– Defining disease under study
– Describing distribut...
• Def the population
– Age , sex, occupation, culture, characteristics
n similar information
– Population should be large ...
• Def the disease under study
– Precise and valid
– Operational defined…. Identified n measured
• Describing the disease
–...
– Place distribution – b/w countries
• Genetic Vs environment
• Role of diet
• Migration changes
• Geographic variations
–...
• Measurement of disease :
– Mortality-
– Morbidity-
• incidence – longitudinal stud.
• prevalence - cross sectional stud....
• Formulation of hypothesis
• Should specify :
– The population
– Specific cause
– Expected outcome
– Dose response relati...
• Uses :
– Data regarding magnitude of disease load
and types of disease problem
– Clues – disease Etiology and helps in
f...
ANALYTICAL STUDYANALYTICAL STUDY
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Analytical studies
• Second major type of study after descriptive
study.
• Interest – individual…instead of population
• T...
CASE-CONTROL STUDIES
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Case-Control Study
• Directionality: Always backwards
• Timing: Always Retrospective
?
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Case-control study design
Exposure Disease Observer
?
Choose groups with and without
disease, look back at what different
...
Case control studies
• Attempt to make inference from
existing observations (retrospective)
• Compares patients with outco...
• Basic steps :
– Selection of cases & controls
– Matching
– Measurement of exposure
– Analysis & interpretation
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Strengths of case-control design
• Best study when have rare disease or
outcome
• Relatively quick and inexpensive
www.ind...
Weaknesses (potential biases)
• Selection (confounding) bias : controls must be as
similar to cases as possible without an...
Ways to combat weakness
• Matching: for each case, find a control
that looks just like him/her in all other
possible ways ...
Types of blinding
• Single blind trial – participant is not
aware whether he belongs to case or
control group.
• Double bl...
Cohort Studies/Prospective
study/ Longitudinal/
Incidence/Forward-looking
study
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Cohort studies
• Studies whether exposure to a “risk factor”
is associated with a subsequent “outcome”
• Select two popula...
• Consideration in assembling cohorts
– Free of disease
– Equally susceptible to disease
– Comparable groups
– Diagnostic ...
Cohort Study
• Directionality: Always forward
Exposure Study Begins Study Begins
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Prospective Cohort study design
Exposure Observer Disease
?
Start with two groups of people who are
exposed and unexposed,...
Cohort Study Design (Retrospective/Historical)
Exposure Disease Observer
?
Start with two groups of people who are exposed...
Prospective vs. Retrospective Cohort
• Prospective: start with exposed and
unexposed groups, wait for the outcome
• Retros...
Strengths of cohort study
• Not only can you look at risk, you can
calculate how many people actually get the
disease (inc...
Some problems with cohorts
• Time consuming
• Large sample size required
• Expensive
• Attrition of study group
www.indian...
1.Selection of study subjects
• General population
• Select group…. Special exposure….
Degree or duration of exposure
2.Ob...
3.Selection of comparisons group
• Internal comparisons… basis of degree /
levels of exposure
• External comparison with g...
5.Analysis
• Incidence rates of outcome among
exposed n unexposed
• Estimate of risk
• Risk estimate done in terms of-
– R...
Relative risk Vs. Attributable risk
• RR is imp in etiological enquires
• Increase in RR … inc cause n effect
association
...
Cross-Sectional Study
• Directionality: Always Non-directional
• Timing: Always Retrospective
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Cross-Sectional Study
Advantages:
• Convenient and inexpensive
• Can consider several exposures and several
diseases
• Can...
Cross-Sectional Study
Disadvantages:
• Cannot establish whether the exposure preceded
disease or disease influenced exposu...
EXPERIMENTAL STUDYEXPERIMENTAL STUDY
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Experimental studies
• Final / definitive step
• Direct intervention
Only Results from Experimental
Studies Can Demonstrat...
The investigator through randomization allocates subjects to
different categories of exposure.
BASIC IDEA
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1. To promote “Scientific Proof” of
aetiological factors.
2. To provide a method of measuring
the effectiveness and effici...
1. ANIMAL EXPERIMENTS
2. HUMAN EXPERIMENTS
CLASSIFICATION OF EXPERIMENTS
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Animal studies are done for the following
purposes
a) Experimental reproduction of human
disease in animals to confirm aet...
1. Animals are bred in laboratories and
manipulated easily according to
wishes of the experimenter.
2. They multiply rapid...
1. All human diseases cannot be
reproduced in animals.
2. Results of animal studies cannot be
extrapolated to human beings...
1. They are done on humans and very much
needed to investigate disease etiology.
2. They are also done to evaluate the pre...
They are broadly divided into two types
1. Randomized Controlled Trials
2. Non Randomized Trials
CLASSIFICATION OF EXPERIM...
RCT is considered as the gold standard
in epidemiology and perhaps the most
concrete evidence for establishing
association...
Types Of Randomized Controlled Trial
CLINICAL TRIAL
- concerned with evaluating therapeutic agents like
drugs.
PREVENTIVE ...
1. Drawing up a protocol
2. Selecting reference and experimental
Populations
3. Randomization
4. Manipulation or Intervent...
Select suitable population
(Reference or Target Population)
Select suitable sample
(Experimental or study population)
Thos...
1. Concurrent Parallel Study
2. Cross-over type of Study
STUDY DESIGNS IN RCT’S
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Patients
Random Assignment Exposed to
specific
Treatment
Unexposed to
specific treatment
Observation
Compare
Outcome
Compa...
1. Researcher has ‘control’ over the
intervention (s).
2. Results are ensured.
3. Reliable and well-respected research
des...
1. Problems in dealing with multiple
causation; isolating individual factors may
over-simplify complex issues.
2. Ethical ...
Ethical aspect
• All innovative scientific interventions, whether
diagnostic, prophylactic, or therapeutic should
ultimate...
International Declarations:
• The first code was “ the Nuremberg
Code of 1947”
• This was followed by the “Declaration of
...
HELSINKI GUIDELINES:
a) Biomedical research should follow scientific principles and
should be based on adequately performe...
f) In any research on humans, each subject be informed
about the aim, methods, benefits and potential
hazards of the study...
HIERARCHY OF EVIDENCE
SYSTEMATIC REVIEWS &
META ANALYSIS
RCTs
LONGITUDINAL COHORT STUDIES
CASE-CONTROL STUDIES
CROSS SECTI...
Meta Analysis
• New concept in research
• Coined by Glass in 1976
“Metanalysis is nothing but combining the
results of sev...
• Like a review article, begins with a
literature review identifying studies of
similar research question.
• Later it atte...
Uses
• It scrutinizes studies to explain why
research results differ
• Identify new direction for research
• Useful in the...
Conclusion
• Thus the study of research procedures and
methods is very important aspect of all post
graduate students and ...
References
• Health research methodology : a guide
for training in research methods
- World Health
Organization
• Preventi...
Thank
You
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Transcript of "Research methodology /certified fixed orthodontic courses by Indian dental academy "

  1. 1. Good MorningGood Morning INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. RESEARCH METHODOLOGY Dr. Murtuza M. Agashiwalawww.indiandentalacademy.com
  3. 3. Contents • Introduction • Research - defn. and types, scientific foundation • Hypothesis – formulation, types • Steps in conducting research • Sampling techniques • Data - types and measuring • Study designs – descriptive, analytical, experimental • Ethical issues • Matching and Bias – types, prevention • Evidence based hierarchy • Metanalysis • Conclusion • References www.indiandentalacademy.com
  4. 4. Introduction Why do Research? - To promote basic knowledge. - To develop new treatment modalities. - To inform the public - For effective planning of available resources. - For commercial success. - For intellectual dependence. - As a partial fulfillment to obtain Master’s Degree www.indiandentalacademy.com
  5. 5. • Research is a quest for knowledge through diligent search or investigation or experimentation aimed at the discovery and interpretation of new knowledge. -Health research methodology, WHO. • Research is a careful investigation or inquiry specially through search for new facts in any branch of knowledge. -Advanced learners dictionary. • Research is a systematized effort to gain new knowledge - Redman and Mory DEFINITION OF RESEARCH www.indiandentalacademy.com
  6. 6. RESEARCH METHODOLOGY 1. Is a way to systematically solve the research problem 2. It may be understood as a science of studying how research is done systematically 3. It not only involves research methods but also extends to consider the logic behind the methods www.indiandentalacademy.com
  7. 7. TYPES OF RESEARCH All research can be broadly classified into two types: 1. BASIC Vs APPLIED 2. OBSERVATIONAL Vs EXPERIMENTAL 3. QUALITATIVE Vs QUANTITATIVE 4. CONCEPTUAL Vs EMPIRICAL www.indiandentalacademy.com
  8. 8. BASIC Vs APPLIED • Basic research is also called fundamental research. It is a search for knowledge without a defined goal of utility or purpose. • Applied research is problem oriented and it is directed toward a defined and purposeful end. It is done based on a perceived need and helps in solving an existing problem. www.indiandentalacademy.com
  9. 9. OBSERVATIONAL Vs EXPERIMENTAL RESEARCH • There are fundamentally two ways in which research questions can be answered:- • We can observe what naturally happens in the real world without interfering with it. ( OBSERVATIONAL) OR • We can manipulate some aspect of the environment and observe its effects ( EXPERIMENTAL) www.indiandentalacademy.com
  10. 10. • Qualitative research deals with subjective aspects which are qualitative or qualities by nature which are difficult to quantify. Eg: Motivation research. • Quantitative research is based on the measurement of quantity or amount. It deals with objective aspects. Eg: Material science research QUALITATIVE Vs QUANTITATIVE www.indiandentalacademy.com
  11. 11. CONCEPTUAL VS EMPIRICAL CONCEPTUAL Research is that related to some abstract idea or theory. It is generally used by philosophers and thinkers to develop new concepts or Re-interpret the existing ones EMPIRICAL Research is that in which experience or observation alone are the tools of research. It is data-based research and it can be further verified by observation or experimentation. www.indiandentalacademy.com
  12. 12. SCIENTIFIC FOUNDATIONS OF RESEARCH 1) Order 2) Inference & chance 3) Maintenance of probability 4) Hypotheses www.indiandentalacademy.com
  13. 13. ORDER Research employs an organized observation of entities or events which are classified or ordered on the basis of common properties & behaviors. The commonality among the observations help in predictions which carry to the ultimate become laws. www.indiandentalacademy.com
  14. 14. INFERENCE & CHANCE Reasoning or inference is the force of advance in research. There are two distinct approaches in the development of inferences DEDUCTIVE – It moves from the general to the specific. Hence it does not allow for the element of chance. It is not used much in health research. INDUCTIVE – It moves from specific to the general. There is extrapolation of results from a sample to the target population. Health research depends almost entirely upon inductive reasoning. Hence chance must be fully accounted for. www.indiandentalacademy.com
  15. 15. MAINTENANCE OF PROBABILITY Maintaining a very high probability & eliminating the chance occurrence is critical to ensure the validity of a research. Techniques used to maintain high probability are- 1. Representative sampling 2. Randomization in selection of study groups 3. Maintenance of comparison groups as controls 4. Blinding procedures 5. Statistical methods www.indiandentalacademy.com
  16. 16. Hypothesis is defined as a presumption, supposition or assumption derived either out of observation or reflection. Hypothesis are carefully constructed statements generated from inferences & they use argument of induction. HYPOTHESIS www.indiandentalacademy.com
  17. 17. METHODS OF GENERATING HYPOTHESIS Mill’s canons of inductive reasoning are frequently utilized in the forming of hypothesis. It involves following methods- 1. The method of difference 2. The method of agreement 3. The method of concomitant variation 4. The method of analogy www.indiandentalacademy.com
  18. 18. MILL’S CANONS OF INDUCTIVE REASONING 1.Method of difference: When the frequency of a disease is markedly dissimilar under two circumstances and if a factor can be identified in one circumstance and not in the other, then this factor either its presence or absence may be the cause of the disease. e.g.: Lung cancer and Smoking Fluoride in water and Caries. www.indiandentalacademy.com
  19. 19. 2. Method of agreement: If a factor’s presence or absence is common to number of circumstances that are found to be associated with the disease then that factor may be causally associated with disease. E.g.: Hepatitis A associated with patient contact, crowding, poor sanitation etc. www.indiandentalacademy.com
  20. 20. 3. Method of concomitant variation; ( Dose Response effect) Eg. Decreasing level of Iodine, with increasing expression of Goiter. Increasing level of Radiation resulting in increase in number of Leukemia cases. www.indiandentalacademy.com
  21. 21. 4. Method of analogy The distribution and frequency of a disease or effect may be similar enough to that of some other disease to suggest commonality in cause. Eg. Hepatitis B virus infection and cancer of the liver. www.indiandentalacademy.com
  22. 22. Formulation of hypothesis • Should specify : – The population – Specific cause – Expected outcome – Dose response relationship – Time response relationship www.indiandentalacademy.com
  23. 23. EXAMPLE OF HYPOTHESIS • E.g. ‘cigarette smoking causes lung cancer’ – incomplete • ‘the smoking of 30-40 cig/day causes lung cancer in 10% of smokers after 20 yrs of exposure’ www.indiandentalacademy.com
  24. 24. I.  Directional hypothesis  Non directional hypothesis II.  Research hypothesis  Null hypothesis III.  Simple hypothesis  Complex hypothesis TYPES OF HYPOTHESIS www.indiandentalacademy.com
  25. 25. 1.Directional hypothesis Is one that specifies not only the existence but the expected direction of the relationship between variables. E.G - Higher the anterior overjet higher the chances of anterior teeth fracture. www.indiandentalacademy.com
  26. 26. 2.Non directional hypothesis Does not stipulate the direction of the relationship. A. There is an association between the degree of anterior overjet and anterior teeth fractures. www.indiandentalacademy.com
  27. 27. 1.Research hypothesis (substantive or scientific hypotheses): Are statements of actual expected relationships between variables. Those which indicate researchers true expectations. Eg; Higher the daily intake of refined sugars higher the DMFT score in children 2.Null hypothesis ( statistical hypothesis) state that there is no relationship between the independent variables and dependent variables. Eg; there is no relationship between daily intake of refined sugars and DMFT score in children www.indiandentalacademy.com
  28. 28. 1.Simple hypothesis: A hypothesis can predict the relationship between a single independent variable and a single dependent variable. 2.Complex hypothesis: It can predict a relationship between two or more independent variables or two or more dependent variables. www.indiandentalacademy.com
  29. 29. E) DATA COLLECTION by 1.Mere Observation 2.Intervention followed by observation PROCEDURAL STEPS IN CONDUCTING RESEARCHPROCEDURAL STEPS IN CONDUCTING RESEARCH A) CONCEPTUALIZING THE PROBLEM Need Background Rationale B) FORMULATING THE OBJECTIVES Generating hypotheses Testing hypotheses C) DESIGNING THE APPROACH Research design Methods and materials D) DEFINING THE POPULATION Target population Study population F) ANALYSIS & INTERPRETATION OF RESULTS G) REPORTING OR PUBLICATION OF THE STUDYwww.indiandentalacademy.com
  30. 30. Sampling • Sampling is the process or technique of selecting a sample of appropriate characteristics and adequate size. • The individuals, records, units or time are considered to be elements in the sample. • An element is the unit of observation or unit about which information is collected and which is the subject of analysis. www.indiandentalacademy.com
  31. 31. Sampling • The total of the elements of the population under the survey is called “sampling frame”. • The sample is drawn from this survey population and is subset of the sampling frame. • The sampling frame may be used in toto for sampling (simple random sampling) or may be divided into sub-groups or strata decided by age, sex, class (stratified sampling); or the frame may consist of areas or clusters of big units containing smaller units ( cluster & multistage sampling). www.indiandentalacademy.com
  32. 32. Advantages of Sampling: 1) Sampling reduces the cost of investigation, the time required and the number of personnel involved. 2) Sampling is especially important when the tests used are highly technical or detailed or must be administered or interpreted by experts. 3) Sampling allows thorough investigation of the units of observation. 4) It is obvious that a sample can be covered more adequately and in more depth in a research project than can a total population. Therefore, Sampling is a more cost efficient way of collecting data. www.indiandentalacademy.com
  33. 33. Requisites for a Reliable Sample 1) Efficiency - Ability of the sample to yield the desired information. 2) Representativeness - inferences drawn from the sample can be generalized to that population with measurable precision and confidence. 3) Measurability - The design of the sample should be such that valid estimates of its variability can be made. In other words, the investigator should be able to estimate the extent to which the findings from the sample are likely to differ from what we would have found had we studied the entire parent population. 4) Size - A sample should be large enough to minimize sample variability to allow estimates of the population characteristics to be made with measurable precision. www.indiandentalacademy.com
  34. 34. 5) Coverage - Adequate coverage of the sample is essential if it is to remain representative. High rates of refusal, unavailability, loss of follow up and other missing data can render a sample unrepresentative of the parent population. 6) Goal Orientation - Sample selection and estimation procedures should be oriented towards the study objectives and research design and considerations. 7) Feasibility - The design should be simple enough to be carried out in practice. 8) Economy and Cost Efficiency - The sample should therefore yield the desired information within expected but tolerable limits of sampling error for the lowest cost. Requisites for a Reliable Sample www.indiandentalacademy.com
  35. 35. Sampling Procedure Probability samples Non-Probability samples www.indiandentalacademy.com
  36. 36. Probability samples Probability samples are those in which it is possible to ascertain the probability that a unit of the population is included in the sample. The common types of probability samples are :- i) Simple Random Sampling - It guarantees that each member of the population has an equal chance of being included in the sample. •The two common methods of random sampling are lottery and tables of random numbers. • The lottery method assigns numbers to the population; these numbers are then thoroughly mixed and a sufficient number drawn (without replacement) to provide the desired sample size. •Tables of random numbers are used after numbers (eg- sequential counts) have been assigned to members of the study population. www.indiandentalacademy.com
  37. 37. ii) Systematic Sampling- The first unit is chosen at random and then other units for the sample are chosen in a systematic way. eg:- every other person or every fifth person. iii) Stratified Random Sampling- It is obtained by using the following procedure:- The population to be sampled is divided into groups known as strata, such that each group is homogeneous in its characteristic. A simple random sample is then drawn from each stratum. This type of sampling is used when the population is heterogeneous with regard to the characteristic under study. Eg:- population divide into different age groups and then samples are selected from the groups randomly. This method ensures more representativeness, provides greater accuracy and can concentrate on wider geographical area. Care must be taken while dividing the population into strata.www.indiandentalacademy.com
  38. 38. iv) Cluster Sampling- It involves choosing groups of units or clusters at random. All the units in each group, or samples of them are then used in the study. Eg:- villages, wards, school children. This method is simpler and involves less time and cost, but gives a higher standard error. v) Multistage Sampling- The first step is to select the groups or clusters. Then the sub samples are then taken in as many subsequent stages as necessary to obtain the desired sample size. E.g.:- choice of states within countries --- 4 Choice of districts within states --- 4 and so on. www.indiandentalacademy.com
  39. 39. vi) Multiphase Sampling- It is used to take basic data from a large sample and details from sub sample. This is different from multistage sampling, in which the same amount of information is obtained for every unit. www.indiandentalacademy.com
  40. 40. Non probability sampling i) Accidental or incidental sampling – people who have assembled in a common place with a common interest or accidentally are surveyed eg. Diabetes in football match ii) Sequential Sampling- Here a small sample is tested in order to answer certain questions about the population. If the questions are not answered, the number of subjects or units in the sample is increased gradually until conclusions may be drawn. www.indiandentalacademy.com
  41. 41. iii) judgment sampling – Sample selection is based on the judgment of the person entrusted with the job iv) Convenience sampling – Selection is made from available source like telephone directory, automobile registers, cards, stock exchange directory etc. www.indiandentalacademy.com
  42. 42. • Discrete:- They are called as attributes. They are qualitative in nature e.g.: Race, Sex, Religion etc. • Continuous:- They are also called variables. They are quantitative in nature. e.g.: Height, weight, RBC’ count etc. TYPES OF DATA www.indiandentalacademy.com
  43. 43. Four principal scales : 1.Nominal scale 2.Ordinal scale 3.Interval scale 4.Ratio scale SCALES OF MEASUREMENT OF DATA www.indiandentalacademy.com
  44. 44. 1. Nominal scale:- This scale uses names or tags to distinguish one measurement from another. It does not imply magnitude of individual measurements. Eg. Classification of sex, Classification of religion. www.indiandentalacademy.com
  45. 45. Ordinal scale:- it is like nominal scale but there exists an implicit graded order relationship among the categories. Eg. Pain measured as: Mild – 1 Moderate – 2 Severe – 3 or Socio economic status measured as Class I Class II Class III Class IV Stages of cancer as I, II, IIIa, IIIb & IVwww.indiandentalacademy.com
  46. 46. • Interval scale: A numerical unit of measurement is used in this scale. The difference between any two measurements can be clearly identified in terms of an interval between two points of scale. This scale has no true zero point Eg. Measurement of body temperature in degrees of Celsius. www.indiandentalacademy.com
  47. 47. Ratio scale • It is as same as interval scale in every aspect except that measurement begins at a true or absolute zero. eg. Weight in Kgs, Height in Mts. There cannot be negative measurements. www.indiandentalacademy.com
  48. 48. EPIDEMIOLOGY EPI = AMONG DEMOS = PEOPLE LOGOS = STUDY DEFINITION OF EPIDEMIOLOGY "Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems." (Last, 1988) -WORLD HEALTH ORGANIZATION www.indiandentalacademy.com
  49. 49. Classification of studies •Descriptive study •Analytical study Cross sectional studyCross sectional study Case control studyCase control study Cohort- follow upCohort- follow up Observational study Experimental study •Randomised control trials/ clinical trials • field trial/ community intervention trial •Community trial All these study complement each other www.indiandentalacademy.com
  50. 50. www.indiandentalacademy.com
  51. 51. Design Options • Directionality • Timing www.indiandentalacademy.com
  52. 52. Directionality • When the exposure variable is observed relative in time to when the health outcome is observed. www.indiandentalacademy.com
  53. 53. Forward Directionality www.indiandentalacademy.com
  54. 54. Backwards Directionality www.indiandentalacademy.com
  55. 55. Non-Directionality www.indiandentalacademy.com
  56. 56. Timing • Timing concerns whether the health outcome of interest, and therefore all study events, has already occurred before the study actually began. www.indiandentalacademy.com
  57. 57. Retrospective www.indiandentalacademy.com
  58. 58. Prospective www.indiandentalacademy.com
  59. 59. DESCRIPTIVE STUDYDESCRIPTIVE STUDY www.indiandentalacademy.com
  60. 60. Descriptive study • Allows…formulation of hypothesis… • 1st phase of an investigation They ask the question – When…time dist – Where…place dist – Who… person dist www.indiandentalacademy.com
  61. 61. • Procedure in descriptive study – Defining population to be studied – Defining disease under study – Describing distribution by time, person n place – Measurement of disease – Comparing with known indices – Formulation of etiological hypothesis Descriptive study www.indiandentalacademy.com
  62. 62. • Def the population – Age , sex, occupation, culture, characteristics n similar information – Population should be large enough – Stable of migration – No visitors n relative Provide denominator for calculating rates, measurement of frequency, distribution n determination of disease Descriptive study www.indiandentalacademy.com
  63. 63. • Def the disease under study – Precise and valid – Operational defined…. Identified n measured • Describing the disease – Distribution…time, place , person – Time trends or fluctuations • Short term fluctuation • Periodic fluctuation • Long term fluctuation Descriptive study www.indiandentalacademy.com
  64. 64. – Place distribution – b/w countries • Genetic Vs environment • Role of diet • Migration changes • Geographic variations – Person distribution – natural history of disease. Descriptive study www.indiandentalacademy.com
  65. 65. • Measurement of disease : – Mortality- – Morbidity- • incidence – longitudinal stud. • prevalence - cross sectional stud. – Disability • Comparing with known indices Descriptive study www.indiandentalacademy.com
  66. 66. • Formulation of hypothesis • Should specify : – The population – Specific cause – Expected outcome – Dose response relationship – Time response relationship • E.g. ‘cigarette smoking causes lung cancer’ – incomplete • ‘the smoking of 30-40 cig/day causes lung cancer in 10% of smokers after 20 yrs of exposure’ Descriptive study www.indiandentalacademy.com
  67. 67. • Uses : – Data regarding magnitude of disease load and types of disease problem – Clues – disease Etiology and helps in formulation of hypothesis – Background data – P, O & E curative services – Describe variation in disease occurrence by time, place and person Descriptive study www.indiandentalacademy.com
  68. 68. ANALYTICAL STUDYANALYTICAL STUDY www.indiandentalacademy.com
  69. 69. Analytical studies • Second major type of study after descriptive study. • Interest – individual…instead of population • Test a hypothesis – Determine Statistical association – Strength of association • 2 types : – Case control study – Cohort study www.indiandentalacademy.com
  70. 70. CASE-CONTROL STUDIES www.indiandentalacademy.com
  71. 71. Case-Control Study • Directionality: Always backwards • Timing: Always Retrospective ? www.indiandentalacademy.com
  72. 72. Case-control study design Exposure Disease Observer ? Choose groups with and without disease, look back at what different exposures they may have had www.indiandentalacademy.com
  73. 73. Case control studies • Attempt to make inference from existing observations (retrospective) • Compares patients with outcome/disease with those without and attempts to identify factors that influenced that outcome (or caused that disease) • Important concept: start with the result (disease) and work backwards for the cause www.indiandentalacademy.com
  74. 74. • Basic steps : – Selection of cases & controls – Matching – Measurement of exposure – Analysis & interpretation www.indiandentalacademy.com
  75. 75. Strengths of case-control design • Best study when have rare disease or outcome • Relatively quick and inexpensive www.indiandentalacademy.com
  76. 76. Weaknesses (potential biases) • Selection (confounding) bias : controls must be as similar to cases as possible without any confounding factors • Berkinsonian bias…rates of adm. to hospital • Recall bias : cases may be able to remember events better because of its significance or may be prompted to remember by investigators • Survival bias: dead people don’t make it into many case-control studies; and if they are alive, they don’t remember things very well • Interviewer’s bias www.indiandentalacademy.com
  77. 77. Ways to combat weakness • Matching: for each case, find a control that looks just like him/her in all other possible ways except for the disease (same age, race, economic class, etc.) • Blinding: individual assessing exposures should be blinded to whether the person is a case or control www.indiandentalacademy.com
  78. 78. Types of blinding • Single blind trial – participant is not aware whether he belongs to case or control group. • Double blind trail – neither doctor nor participant • Triple blind trial – participant, doctor and the person analyzing data www.indiandentalacademy.com
  79. 79. Cohort Studies/Prospective study/ Longitudinal/ Incidence/Forward-looking study www.indiandentalacademy.com
  80. 80. Cohort studies • Studies whether exposure to a “risk factor” is associated with a subsequent “outcome” • Select two populations who seem the same except for the hypothesized risk factor • Follow them and see how many have the outcome or disease • Important concept: Start with the risk, then look for the outcome www.indiandentalacademy.com
  81. 81. • Consideration in assembling cohorts – Free of disease – Equally susceptible to disease – Comparable groups – Diagnostic n eligibility criteria must be defined before hand www.indiandentalacademy.com
  82. 82. Cohort Study • Directionality: Always forward Exposure Study Begins Study Begins www.indiandentalacademy.com
  83. 83. Prospective Cohort study design Exposure Observer Disease ? Start with two groups of people who are exposed and unexposed, follow them to see who gets disease. www.indiandentalacademy.com
  84. 84. Cohort Study Design (Retrospective/Historical) Exposure Disease Observer ? Start with two groups of people who are exposed and unexposed, find out who got the disease. www.indiandentalacademy.com
  85. 85. Prospective vs. Retrospective Cohort • Prospective: start with exposed and unexposed groups, wait for the outcome • Retrospective: both exposure and outcome have already happened, but groups are still made based on exposed or unexposed www.indiandentalacademy.com
  86. 86. Strengths of cohort study • Not only can you look at risk, you can calculate how many people actually get the disease (incidence rates) • Since you enroll subjects before the outcome, you can measure multiple exposures without recall bias • Best for rare exposures www.indiandentalacademy.com
  87. 87. Some problems with cohorts • Time consuming • Large sample size required • Expensive • Attrition of study group www.indiandentalacademy.com
  88. 88. 1.Selection of study subjects • General population • Select group…. Special exposure…. Degree or duration of exposure 2.Obtaining data on exposure • Cohort members • Review of records • Medical examination/special tests • Environmental surveys Steps of Cohort study www.indiandentalacademy.com
  89. 89. 3.Selection of comparisons group • Internal comparisons… basis of degree / levels of exposure • External comparison with general population • Periodic medical examination • Reviewing physician n hospital records • Surveillance of death record • Mailed questionnaires, tele calls 4.Follow - up www.indiandentalacademy.com
  90. 90. 5.Analysis • Incidence rates of outcome among exposed n unexposed • Estimate of risk • Risk estimate done in terms of- – Relative risk … strength of association b/w risk factor n disease – Attributable risk • In diff in incidence rates of disease b/w exposed grp n non exposed • Extent the disease under study can be attributed to exposure www.indiandentalacademy.com
  91. 91. Relative risk Vs. Attributable risk • RR is imp in etiological enquires • Increase in RR … inc cause n effect association • AR .. Impact of successful preventive or public health programme on the problem www.indiandentalacademy.com
  92. 92. Cross-Sectional Study • Directionality: Always Non-directional • Timing: Always Retrospective www.indiandentalacademy.com
  93. 93. Cross-Sectional Study Advantages: • Convenient and inexpensive • Can consider several exposures and several diseases • Can generate hypotheses • Usually represents the general population www.indiandentalacademy.com
  94. 94. Cross-Sectional Study Disadvantages: • Cannot establish whether the exposure preceded disease or disease influenced exposure • Can identify only prevalent cases rather than incident cases • Possible bias since only survivors are available for study • May under-represent diseases with short duration www.indiandentalacademy.com
  95. 95. EXPERIMENTAL STUDYEXPERIMENTAL STUDY www.indiandentalacademy.com
  96. 96. Experimental studies • Final / definitive step • Direct intervention Only Results from Experimental Studies Can Demonstrate Cause and Effect Relationships www.indiandentalacademy.com
  97. 97. The investigator through randomization allocates subjects to different categories of exposure. BASIC IDEA www.indiandentalacademy.com
  98. 98. www.indiandentalacademy.com
  99. 99. 1. To promote “Scientific Proof” of aetiological factors. 2. To provide a method of measuring the effectiveness and efficiency of health services. Aims of experimental studies www.indiandentalacademy.com
  100. 100. 1. ANIMAL EXPERIMENTS 2. HUMAN EXPERIMENTS CLASSIFICATION OF EXPERIMENTS www.indiandentalacademy.com
  101. 101. Animal studies are done for the following purposes a) Experimental reproduction of human disease in animals to confirm aetiological hypothesis. b) To test the efficacy of various therapeutic and preventive measures such as vaccines and drugs. c) To study the natural history of disease. Animal experiments are done on carefully bred animals in controlled environments. PURPOSES OF ANIMAL STUDIES www.indiandentalacademy.com
  102. 102. 1. Animals are bred in laboratories and manipulated easily according to wishes of the experimenter. 2. They multiply rapidly and enable experimenter to carry out certain experiments which are not possible in human beings. ADVANTAGES www.indiandentalacademy.com
  103. 103. 1. All human diseases cannot be reproduced in animals. 2. Results of animal studies cannot be extrapolated to human beings. LIMITATIONS www.indiandentalacademy.com
  104. 104. 1. They are done on humans and very much needed to investigate disease etiology. 2. They are also done to evaluate the preventive and therapeutic measures. eg. James Lind (1747) – Study done on Sailors to reveal the association of lemons, oranges in diet on scurvy among a group of Sailors. Edward Jenners (1796) experimental work with Cowpox to develop vaccine against Small pox. 3.Human studies should be carefully designed because they involve logistic and ethical implications HUMAN EXPERIMENTS www.indiandentalacademy.com
  105. 105. They are broadly divided into two types 1. Randomized Controlled Trials 2. Non Randomized Trials CLASSIFICATION OF EXPERIMENTAL STUDIES www.indiandentalacademy.com
  106. 106. RCT is considered as the gold standard in epidemiology and perhaps the most concrete evidence for establishing association. RANDOMIZED CONTROLLED TRIALS www.indiandentalacademy.com
  107. 107. Types Of Randomized Controlled Trial CLINICAL TRIAL - concerned with evaluating therapeutic agents like drugs. PREVENTIVE TRIALS - purported to prevent or eliminate diseases on an experimental basis. RISK FACTOR TRIALS - A trial of risk factors in which the investigator intervenes to interrupt the usual sequence in the development of disease. www.indiandentalacademy.com
  108. 108. 1. Drawing up a protocol 2. Selecting reference and experimental Populations 3. Randomization 4. Manipulation or Intervention 5. Follow-up 6. Assessment of outcome STEPS IN RCT DESIGN www.indiandentalacademy.com
  109. 109. Select suitable population (Reference or Target Population) Select suitable sample (Experimental or study population) Those not eligible Those who do not wish to give consent Make necessary exclusions RANDOMIZE Experimental group Control Group Manipulation & Follow up Assessment DESIGN OF A RANDOMIZED CONTROLLED TRIAL www.indiandentalacademy.com
  110. 110. 1. Concurrent Parallel Study 2. Cross-over type of Study STUDY DESIGNS IN RCT’S www.indiandentalacademy.com
  111. 111. Patients Random Assignment Exposed to specific Treatment Unexposed to specific treatment Observation Compare Outcome Compare Outcome Exposed and Unexposed to treatment CONCURRENT PARALLEL STUDY DESIGN CROSS-OVER TYPE OF STUDY DESIGN Time Patients Random Assignment Exposed to specific Treatment Unexposed to specific treatment Observation Time www.indiandentalacademy.com
  112. 112. 1. Researcher has ‘control’ over the intervention (s). 2. Results are ensured. 3. Reliable and well-respected research design 4. Individual factors can be identified. ADVANTAGES OF EXPERIMENTAL RESEARCH DESIGNS www.indiandentalacademy.com
  113. 113. 1. Problems in dealing with multiple causation; isolating individual factors may over-simplify complex issues. 2. Ethical issues. 3. Researcher bias and subjectivity in research design, methods and analysis. 4. Hawthorne effect upon groups being researched . DISADVANTAGES OF EXPERIMENTAL RESEARCH DESIGNS www.indiandentalacademy.com
  114. 114. Ethical aspect • All innovative scientific interventions, whether diagnostic, prophylactic, or therapeutic should ultimately be evaluated in human subjects • The need for safeguards in human experimentation cannot be overemphasized and several important codes have been developed for protection of human subjects • Three underlying principles are 1. Beneficence, which requires that good should result, harm should be avoided or that benefits should justify the expected risk or harm 2. Respect for rights, including free choice of the subject and protection for those of diminished autonomy 3. Justice, which requires a equal distribution of burden and benefits www.indiandentalacademy.com
  115. 115. International Declarations: • The first code was “ the Nuremberg Code of 1947” • This was followed by the “Declaration of Helsinki” which was adopted by The World Medical Association and the W.H.O in 1975. www.indiandentalacademy.com
  116. 116. HELSINKI GUIDELINES: a) Biomedical research should follow scientific principles and should be based on adequately performed laboratory and animal experimentation. b) The design of each procedure involving humans should be clearly formulated in an experimental protocol. c) the experiment should be conducted by scientifically qualified persons under supervision of medical experts. d) The right of the research subject to safeguard his/ her integrity must always be respected. e) The accuracy of the research results must be preserved. www.indiandentalacademy.com
  117. 117. f) In any research on humans, each subject be informed about the aim, methods, benefits and potential hazards of the study. g) When obtaining informed consent for research, a doctor should be cautious if the subject is in a dependant relationship to him/ her. h) In case of legal competence, informed consent should be obtained from the legal guardian. i) Subjects should be informed that they are free to abstain or to withdraw from participation at any time. HELSINKI GUIDELINES: www.indiandentalacademy.com
  118. 118. HIERARCHY OF EVIDENCE SYSTEMATIC REVIEWS & META ANALYSIS RCTs LONGITUDINAL COHORT STUDIES CASE-CONTROL STUDIES CROSS SECTIONAL STUDIES CASE REPORTSwww.indiandentalacademy.com
  119. 119. Meta Analysis • New concept in research • Coined by Glass in 1976 “Metanalysis is nothing but combining the results of several clinical studies on the same subject to derive definitive conclusions.” www.indiandentalacademy.com
  120. 120. • Like a review article, begins with a literature review identifying studies of similar research question. • Later it attempts to analyze statistically the aggregate results to derive a single integrated question www.indiandentalacademy.com
  121. 121. Uses • It scrutinizes studies to explain why research results differ • Identify new direction for research • Useful in the research of rare diseases • Decides on the best clinical approach to the problem www.indiandentalacademy.com
  122. 122. Conclusion • Thus the study of research procedures and methods is very important aspect of all post graduate students and at the same time provide guidelines on which our future research would be based. • It also shows us the procedures that need to be followed while undertaking research and also shows us, how the data or findings of our study should be presented for correct interpretation and for publication. www.indiandentalacademy.com
  123. 123. References • Health research methodology : a guide for training in research methods - World Health Organization • Preventive and social medicine - K. Park • Essentials of preventive and community dentistry - Soben Peter • Methods of biostatistics - T Bhaskara Rao www.indiandentalacademy.com
  124. 124. Thank You www.indiandentalacademy.com For more details please visit www.indiandentalacademy.com

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