Study design is a specific plan or protocol for the study, which allows to translate into an operational one.

1. Study design
Preparation by :
Mohammed Ahmed
Farah Tahir
Ameen Nabiel
Supervisor
Ass. Prof. Ban Nadhum Abdul-Fatah
University of Anbar
College of Medicine
Department of Microbiology
2023-2024

2. Study Design
Study design is a specific plan
or protocol for the study, which
allows to translate into an
operational one.

3. Types of Study Designs
Observational Studies Experimental Studies
Observe and record data
without intervention.
Allows for cost-effective
study of large
populations.
Randomly assign
participants and compare
outcomes to establish
cause-and-effect
relationships.

4. Choosing the Right Study Design
The best study design for a research question depends on various
factors including the type of information required, available resources,
and the ethical considerations involved. Consider these tips to make
the right decision:
1 Research Question
What type of information are you trying
to obtain?
2 Resources
How much time and money do you have
to devote to the study?
3
Are there any potential risks to the
participants?
4 Consultation
Consult with a statistician or research
methodologist to get help choosing
a study design.
Ethical Considerations

5. Common Types of Observational
Studies
1 Cross-Sectional Studies
Measure prevalence of disease or risk factor at one point in
time through surveys and interviews.
2 Case-Control Studies
Compare cases and controls to identify risk factors for a
disease or outcome.
3 Cohort Studies
Follow a group of people over time to observe incidence
of disease or outcome.

6. Cross-Sectional Studies
Definition
Measure prevalence of
disease or risk factor
at one point in time.
Limitations
Cannot establish cause-
and-effect relationships
and susceptible to
confounding bias.
Example
An institutional survey
to understand the
attitudes of patients
towards a new drug.

7. Case-Control Studies
1 Definition
Compare cases (people with a disease)
and controls (people without a disease) to
identify risk factors.
2 Advantages
Efficient and can be used to study rare
diseases.
3 Disadvantages
Susceptible to confounding bias, cannot
establish cause-and-effect relationships.
4 Example
A case-control study investigating the
association between smoking and lung
cancer.

8. Cohort Studies
1 Definition
Follow a group of people over time to measure
incidence of disease or risk factor.
2 Prospective Cohort
Recruits participants based on exposure status and
follows them to observe the incidence of outcomes.
3 Retrospective Cohort
Uses existing data to identify exposure status and
follows to observe the incidence of outcomes.

9. Strengths of Observational
Studies
Observational studies can provide important insights for understanding diseases
and risk factors in populations. Here are some advantages:
1 Cost-Effective
Observational studies are relatively easy and inexpensive to conduct.
2 Population Studies
Observational studies can be used to study large populations.
3 Rare Diseases
Observational studies can be used to study rare diseases.

10. Randomized Controlled Trials (RCTs)
Definition
Randomly assigns
participants to either a
treatment or control
group to determine the
effect of an
intervention.
Advantages
Can establish cause-
and-effect relationships.
Disadvantages
Expensive and time-
consuming to
conduct, not ethical
for all types of
interventions.
Experimental Studies

11. Advantages and Disadvantages of
Different Study Designs
Understanding the pros and cons of each study design can help you choose the right
one for your research question. Here's a quick summary:
Observational studies
• Advantages: Relatively easy and
inexpensive to conduct, can be
used to study large populations,
can be used to study rare
diseases.
• Disadvantages: Cannot establish
cause-and-effect relationships,
susceptible to confounding bias.
Experimental studies
• Advantages: Can establish cause-
and-effect relationships.
• Disadvantages: Expensive and
time-consuming to conduct, not
ethical for all types of
interventions.

12. Why Choose a Well-Designed Study?
Valid Results
Well-designed studies
produce valid and reliable
results, leading to accurate
conclusions.
Efficient Research
A well-designed study
optimizes resources and
ensures the research
process runs more
effectively and smoothly.
Ethical Considerations
Well-designed studies
minimize risks to
participants and ensure the
ethical standards are met.

13. Conclusion
Choosing the right study design is critical in
ensuring the validity and reliability of research
results. Consider the research question,
resources, and ethical considerations when
making this decision.