1

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

3

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.

4

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).

5

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.

6

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.

7

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.

8

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.

9

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

10

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

11

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.

12

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

13

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

14

15

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)

16

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.

17

Types of Research

According to the state of the knowledge about the problem:

EXPLORATORY RESEARCH

DESCRIPTIVE RESEARCH

EXPRIMENTAL RESEARCH

18

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

19

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

20

IN RELATION TO THE PERIOD

OF DATA COLLECTION

21

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

22

IN RELATION TO THE PERIOD

OF DATA COLLECTION

23

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

24

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

25

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

26

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.

27

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.

28

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.

29

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.

31

What is a Cross sectional study design?

A cross sectional design may make it

difficult to establish what is cause and what

is effect

32

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?

33

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.

34

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

35

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.