The major issues that must be examined when developing research methods are: Study area and period Study design Population Sample size and sampling techniques,

V. METHODS AND MATERIALS
12/16/2023 1
MPH @JJU, by M. Omar
By: Mohamed Omar (Asst. Prof)

Learning Objectives
At the end of the session you should be able to:
1. Identify the pertinent questions to consider
when developing the methodology of a
research proposal
2. Describe and understand the various
components of the methods section
3. Explain the cyclical nature of the different steps
in designing research methodology
4. This describes the steps to be traced in
achieving the objective
12/16/2023 2

Methods
 Now we have to decide exactly how we are going to
achieve our stated objectives
 Where should we collect it? Study area
 What new data we need to shed light on the problem?
 Data collection and process.
 What new information do we need? Selection of
variables
 How will we collect this information?
 Selection of type of study Design
 What tools do we need to collect it?
 Selection of data collection techniques
12/16/2023 3

Cont….
 How many subjects do we include in the study
and how do we select them?
 Sampling
 Populations
 How do we collect the data?
 Plan for data collection
4
12/16/2023 MPH @JJU, by M. Omar

Cont.…
 What will we do with the collected data?
 Plan for data processing and analysis
 How can we determine whether our methods for data
collection are correct before implementing the study?
 Pretesting the methodology
 Are we likely to harm anyone as a result of the study?
 Ethical considerations
 How much time and money it cost me?
 Resource required
5

Main Components of the methods
• The major issues that must be examined when
developing research methods are:
 Study area and period
 Study design
 Population
 Sample size and sampling techniques,
 Measurement: main variables
 Data collection technique
 Pre-testing
 Data quality assurance
 Data processing and analysis
 Ethical considerations
 Limitations, and
 Operational definitions
 Plan for dissemination of data
12/16/2023 6

Study Area and Period
• Study Area
Brief description of:
 The area (weather, distance, altitude)
 The population,
 The health service directly or indirectly related to
the problem under study,
 Study subjects distribution etc,
• Study period: the period for which the data is
generated or the reference period where the data is
available
12/16/2023 7

Study Design
• It is a specific plan or protocol for conducting the
study which allows the investigator to translate the
conceptual hypothesis into an operational one.
Research question(s) dictates your study design
What do we want to know? (General Objective)
Your research question determines the “how” and
“what” of the research: design and data collection
method(s).
8

Criteria for selecting study design
The type of study design chosen depends on:
 The type of problem,
 The already available knowledge about the
problem, (personal experience)
 Audience
 The resources available for the study.
9

Study design Based on objectives:
 Descriptive,
 Explanatory and
 Exploratory
10

Problem
Problem exists but
little is known
Contributing factors
to the problem
Establish the extent
of contribution
factors
Sufficient
knowledge about
cause to prevent,
control, or solve the
Question
Nature/Magnitude
of the problem
Who is affected?
How do affected
people behave?
What are the
factors?
What is the cause?
Will the removal of
a factor prevent or
reduce the
problem?
What is the effect
of a particular
intervention
Design
Exploratory/Descriptive
Descriptive case study
Cross-sectional survey
Analytical (Comparative)
Cross-sectional-
comparative
Case-control
Cohort
Experimental/quasi
Experimental study
design
Experimental/quasi
Experimental study
design
11

Based on Design
1. Observational (Non-intervention studies)
Describes and analyzes researchable objects or
situations but does not intervene
Cross sectional, cohort and case control study
2. Intervention studies (Experimental)
Manipulates objects or situations and measures
the outcome of the manipulations
Randomized Clinical Trial (RCT), Community
Intervention Trial (CIT)
Quasi-experimental
12/16/2023 12

Case-control
Cohort
Individuals
Intervention
Retrospective
Prospective
Descriptive
Populations
Analytical
Observational
Case-
series
Cross-sectional
Ecologic
al
Clinical trials
Epidemiological study designs
12/16/2023 13
Case-report

Design Based on approach
1. Quantitative
2. Qualitative
3. Mixed
14

Population
 A group of individuals, objects, or items from
among which samples are taken for
measurement.
 Decisions must be made concerning the
population or individual units (persons,
households, etc.) to be investigated
 The population under consideration should be
clearly and explicitly defined in terms of place,
time, and other relevant criteria
16

Source population
 Those are the general population from which
the study subjects are selected
 Identify on whom to do the research.
 Think to whom the study result would be
inferred or concluded.
12/16/2023 17

Reference Population
Source Population
Sampling Frame
Sample
Study Subjects
Jigjiga district School
Children
School children in Jigjiga
District Schools
Class (Student)
Registers of schools
Each 20 students
randomly selected from
each class in each
Schools in Jigjiga
Students who provide
information to the
research team
Schematic figure to illustrate sampling
12/16/2023 18

Study population (Subjects):
These are subjects that would be selected for
the study.
i.e, these are people in which if they got the chance
of being selected would be enrolled in the study).
They are identified and selected from the
Source Population by using both inclusion
and/ or exclusion criteria of being a study
subject.
12/16/2023 19

Inclusion and exclusion criteria
• Inclusion: Segment of population that will be
included into the study by sampling methods
• Exclusion criteria: special segment of
population which are excluded from the selection
due to different reasons.
– Eg. Severely sick, unable to communicate, Etc….
• NB: Be careful about ethical issues
• Non- response: individual who refused to
participate in to the study from the beginning or
refused and drop from the study before
completing the survey
20

Practical questions in selecting population
• Is the proposed population the one that would give
the required information?
• Will the population cooperate to participate in the
study, or will it be a 'resistant' one?
• If it is proposed to study patients with a specific
disease, will it be possible to identify enough cases
to yield useful conclusions?
• If a long term 'follow up' study is planned, is the
population so mobile that it may be difficult to
maintain contact with the subjects?
21

Sample size and sampling
procedure
12/16/2023 22

Sampling
• The population is too large to collect
information from all members
• Instead, select a sample of individuals hoping
that the sample is representative of the
population
• Sampling: The selection of a number of study
units from a defined study population
23

Sampling…
• Possible questions:
 What is the group of people (study population)
from which we want to draw a sample?
 How many people do we need in our sample?
 How will these people be selected?
– Sampling unit: is the unit of selection in the sampling
process ,e.g. in a sample of districts: a district
– Study unit: is the unit on which the observations will be
collected, e.g. in a study of family size: Households
24

Sampling…
 Sample design: The scheme for selecting the
sampling units from the study population
 Representativeness: to draw conclusions that
are valid for the whole study population draw a
sample in such a way that it is representative
of that population
 A representative sample has all the important
characteristics of the population from which it is
drawn
25

Exercise
• To Assess KAP towards modern contraceptive use
in kebribayah district
- Which study design is appropriate?
- Who is your study population?
- What is your sampling unit?
- What is your study unit?
- How do you select your sample?
• Individual assignment to be submitted on next
Friday via email: mahamadwehliye@gmail.com.
You should explain why you give the answer for
each question.
26

Sample size
• Sample size determination depends on the:
– Objective of the study
– Design of the study
– Plan for statistical analysis
– Accuracy of the measurement to be made
– Degree of precision required for generalization
– Degree of confidence with which to conclude
12/16/2023 27

Sample size
 For cross-sectional study
– Single proportion and mean sample size
determination is used
n = sample size
Zά/2 = Z value at (∞ = 0.05) = 1.96
P = Proportion of occurrence of the event to be
studied.
(Usually found from literature review).
D = Margin of error (Precision), (Usually < 0.05)
12/16/2023 28

Sample size determination
• How many subjects are needed in the sample to enable
draw conclusion on the whole population?
– Depends on expected variation in the data and number of
units per cell for analysis
– The eventual sample size is a compromise between what
is desirable and what is feasible
– If the sample is to be taken from a relatively small
population (N<10,000): Sample size should be corrected nf
= n/(1+n/N)
– In multistage sampling, design effect is required
12/16/2023 29

Design effect
• This provides a correction for the loss of
sampling efficiency resulting from the use of
cluster sampling instead of simple random
sampling
• The magnitude of DE depends upon two
factors:
– The degree of similarity or homogeneity of elements
within clusters, and
– The number of measurement units to be taken from
each cluster.
– WHO Design effect is 1.5,2, 3 etc 30

Allowance for non-response
• Non-response is a fact of life in surveys. Although
efforts to minimize the level of non-response are
strongly encouraged
• Allowances for non-response are customarily
made during the calculation of sample size
requirements.
• Allowance of 10 percent should prove adequate
in most situations
31

12/16/2023 MPH @JJU, by M. Omar 32

The major issues that must be examined when developing research methods are: Study area and period Study design Population Sample size and sampling techniques,

Recommended

Recommended

More Related Content

Similar to The major issues that must be examined when developing research methods are: Study area and period Study design Population Sample size and sampling techniques,

Similar to The major issues that must be examined when developing research methods are: Study area and period Study design Population Sample size and sampling techniques, (20)

Recently uploaded

Recently uploaded (20)

The major issues that must be examined when developing research methods are: Study area and period Study design Population Sample size and sampling techniques,