huda basaleem khaled abdulla...
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HUDA BASALEEM
Khaled Abdulla Al-Sakkaf
Dept. of Community Medicine
Faculty of Medicine and Health Sciences
University of Aden
At the end of this lecture, trainees will be able to: Identify the different sections of study methods.
Determine the study variables and their types
Implement the appropriate sample type for the
study
Analyse the different type of study design 2
Objectives
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IV. RESEARCH METHODS
The set of clearly and fully expressed rules and procedures, upon which research is based and against which claims for knowledge is evaluated.
The research methodology includes: The study population and the study area. The study variables. The study design. Sampling. Methods of data collection, analysis and
interpretations.
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The Study Population and the Study Area
The group of individual units (whether they are persons, families, medical records, certificates, nursery, specimens of milk, mothers of under five children…etc) to be investigated.
The population should be identified in terms of: Place (the study area).
Time, and demographic characteristics.
A community-based study or hospital-based study.
Will sampling be used? If so, how will the selection from the study population be done? If a sample is chosen, the group or population from whom it is selected may be called the (study population), the (sampled population), or the (parent population).
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Specific Features of the Study population
Volunteer population.
Hospital or clinic population.
Patients notified as having a disease.
Autopsy population.
Groups characterized by their behavior or occupation
Population in which the same individuals appear more than once.
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Inclusion and Exclusion Criteria
Clearly stated criteria must be laid out for including subjects in the study.
The case definition should involve: A) Establishment of objective criteria for the
diagnosis of the disease.
B) A statement of eligibility criteria for the selection of the individuals.
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Inclusion and Exclusion Criteria
Eligibility criteria can be applied either in the selection phase or during the analysis of the study, but preferably should be decided in advance.
Selecting the study population: According
to: Appropriateness. Practicability.
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ACCORDING TO THE TYPE OF VARIABLE
Quantitative (Numerical) Qualitative (or categorical) Continuous Discrete
Age, Weight Blood sugar
No. of cases
No. of specimens
Nominal Ordinal
Marital status, Sex, Nationality
Educational level Degree of burn
Study Variables VARIABLE: a characteristic of a person, object, or phenomenon that can take different values and which is measured.
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obtained by measurement Quantitative Continuous can have any value between 2 values (fraction) obtained by counting or enumeration Quantitative Discrete only integer number Qualitative Nominal groups the element according to the characteristics (cannot be ordered) Qualitative Ordinal ordered arrangement
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Factors rephrased as variables
Factors Variables
Long waiting time Waiting time
Absence of drugs Availability of drugs
Lack of supervision Frequency of supervision
Poor knowledge about the disease
Knowledge about the disease
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Operationalizing variables by choosing
appropriate indicators
It is sometimes not possible to find meaningful categories
unless the variables are made operational with one or more
precise INDICATORS. Opertionalizing variables means
making them „measurable‟. For example: Nutritional status of
under 5-years old.
- Weight in relation to age.
- Weight in relation to height.
- Height in relation to age.
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Defining variables and indicators of
variables
When defining the variable or its indicator, two aspects to be considered:
1- An operational definition A) Conceptual definition: It defines the variable as we conceive
it. B) Operational definition: (or working definition): Defines the
characteristic we will actually measure (in a measurable form).
2- The scale of measurement: 1. Continuous scale 2. Ordinal scale
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Dependent and independent variables:
Dependent variable (outcome): The variable that is used to describe or measure the problem under study.
Independent variable (cause): The variables that is used to cause or at least to influence the problem.
Cause Effect (outcome) (Independent) (Dependent) Other factor (Confounding )
Confounding Variables
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Confounding variable
A variable that is associated with the problem and with a possible cause of the problem.
Mother's education Malnutrition Independent Dependent
Family income (Confounding variable)
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Section Three
The Study Design
The procedures and methods predetermined by an investigator, to adhere to, in conducting a research project.
The type of study design depends on: The type of problem; The knowledge already available about the
problem; and The resources available for the study.
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Types of Research
According to the state of the knowledge about the problem:
EXPLORATORY RESEARCH
DESCRIPTIVE RESEARCH
EXPRIMENTAL RESEARCH
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Types of Research
According to the possibilities of application of the results can be:
FUNDAMENTAL GUIDED
RESEARCH
FUNDAMENTAL BASIC RESEARCH New knowledge and
technologies
APPLIED RESEARCH Priority problems, policy, programs –
health benefits
Exploratory
Conducted for the purpose of generating preliminary data
Descriptive: Retrospective, Prospective Longitudinal, Transversal
Population Individual
Nonintervention - Analytic
Observational Experimental
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Types of Research (According to the objectives)
Intervention or experimental
Nonintervention or Observational
Exploratory Descriptive Analytical
Case study/ case serial Cross-sectional
Case-control
Cohort study
Quasi-experimental
Experimental
-Random control-trial -Field Trial -Community Trial
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IN RELATION TO THE PERIOD
OF DATA COLLECTION
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Retrospective.
A phenomenon is studied after that have already happened.
Usually uses established registers and medical records.
Prospective.
Study the phenomenon in the same time of the occurrence.
Longitudinal.
When it is studied an event during a period of time.
Example: Evolution of patients with any disease. Transversal. Cross sectional.
When the phenomenon is studied in a given moment, as a photo. Example: Census
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IN RELATION TO THE PERIOD
OF DATA COLLECTION
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OVERVIEW OF STUDY TYPES
Nonintervention
(Observational)
Intervention
(Experimental)
The researcher describes and analyzes but doesn‟t intervene
The researcher manipulates and measures the outcome
of this manipulation
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Intervention Nonintervention
Exploratory Descriptive Analytical
•Case report or case series •Cross-sectional surveys •Ecological studies
•Cross-sectional comparative studies •Case –control study •Cohort study
Experimental
Quasi-experimenta
l
•Randomized controlled (clinical) trial •Field trials • Community trials
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Is a small-scale study of relatively short duration, which is carried out when little is known about a situation or a problem.
This type of study try to give answer on a specific question on relation to the nature of the problem.
Exploratory study
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Exploratory study
For example: the National Control programme on AIDS,
would like to implement a counselling services to help
the infected people, but no enough information exist on
the needs of the patients.
Therefore for exploring these needs, interviews were
conducted with patients (males, females, single or
married).
The obtained information have described the needs of the
different groups and facilitates the proper work with each
group.
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Descriptive study
The systematic collection and presentation of data to give a clear picture of a particular situation.
Describes the general characteristics of a disease in relation to person, place, and time.
Characterize factors related to host, agent, and environment; or characterize exposure and susceptible status.
Enable us to develop hypothesis about that disease pattern.
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1. Case report or case series
Describe in-depth the characteristics of one or a limited number of cases.
Describe clinical observations, interesting or
unusual variations of disease, results of new treatment modalities, and to call attention to unexpected findings.
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2. Cross-sectional surveys
Aim at quantifying the distribution of certain variables in a study pop. at a point of time.
Cross-sectional survey may cover: - Physical characteristics of people, materials or the environment as in: - Prevalence surveys. - Evaluation of coverage, -Socioeconomic characteristics: age, education, marital status, income, etc; -Behavior of people and the knowledge, attitudes, believes, and opinions (KAP studies), -Events that occurred in the population
A cross sectional study measures the prevalence of
health outcomes or determinants of health, or
both, in a population at a point in time or over a
short period.
Such information can be used to explore aetiology -
for example, the relation between cataract and
vitamin status has been examined in cross
sectional surveys. 30
What is a Cross-sectional study design?
If milk drinking is associated with peptic ulcer, is that
because milk causes the disease, or because ulcer
sufferers drink milk to relieve their symptoms?
Because of these difficulties, cross sectional studies of
aetiology are best suited to diseases that produce little
disability and to the pre-symptomatic phases of more
serious disorders.
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What is a Cross sectional study design?
A cross sectional design may make it
difficult to establish what is cause and what
is effect
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In C-S study, research questions usually having the following general form
What is the prevalence of disease X or factor Y in a given population?
How many people in the population have
disease X or factor Y?
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3. Ecological studies (Correlation Studies):
The units of analysis are populations or groups of people rather than individuals.
Compares populations in different countries at the same time or the same population in one country at different times.
The later approach may avoid some of the socioeconomic confounding that is a potential problem in ecological studies.
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Go beyond simply describing the distribution of, or pattern of occurrence of disease, and attempt to analyze the reasons or the risk factors for them.
Hypotheses driven from descriptive studies
may be tested using analytic study methods.
Comparative or Analytical Studies
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1. Cross-sectional comparative studies
Focus on comparing as well as describing groups. For example, a survey on malnutrition may wish to establish:
- The percentage of malnourished children in a certain population;
- Socioeconomic, physical, political variables that influence the problem;
- Feeding practices; and -The knowledge, beliefs and opinions that influence
these practices.
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