2. Core Competencies: Choosing Study Design
Dr. Jackson K. Mukonzo, MSc. Pharm, Ph.D

3. Before starting……..
Is there a problem? – Do you have a research question?
What do you want to do about the problem?
How do you want to do it?

4. Research Design Internal validity as opposed to external validity:
Research Design refers to the plan, structure, and strategy of research--the blueprint that will guide the research process.
Internal validity as opposed to external validity:
Researcher ability to draw, correct/accurate conclusions from the research.

5. Study design: How?
A study design is a specific plan or protocol for conducting the study, which allows the investigator to translate the conceptual hypothesis into an operational one.

6. Choice of Design Research Question(s) Research Goal(s)
Researcher Beliefs and Values
Researcher Skills
Time and Funds
Ethical Limitations
Status of Existent Knowledge
Occurrence of Disease
Duration of Latent Period
Nature and Availability of Information
Available Resources

7. Types of Study Designs Qualitative Quantitative Experimental
Observational
Basic
Hybrid
Incomplete

8. Quantitative No! Qualitative
Are you interested in meaning of experiences or just describing?
Understanding -words and anlysis
Real world experience
Open-ended and flexible rich data
Quality of informant more important than sample size
Subjective
Quantitative
Prediction- discrete
Theory testing (experimental)
Sample size core issue in reliability of data
What you plan for is what get
Objective
Is any of the methods better than the other?
No!

9. Qualitative Techniques
Participant observation
Gains insight into understanding cultural patterns to determine what’s necessary and needed in tool development (complementary to interviews)
Interviews/Focus groups with stakeholders
Explores how tools are used and could be used in a novice programming course
Gains insight into the meaning of tools for students for learning to program

10. Quantitative Designs Analytical Descriptive Experimental Observational
Cohort
Cross-sectional
Case-control
Other
Randomized
Clinical Trial
Non-randomized
Descriptive
Community Survey
A fundamental issue is whether to observe the events taking place in the study subjects in an observational study or to apply an intervention and examine its effects of these events in a clinical trial. Among observational studies, two of the most common designs are cohort studies, in which a group of subjects is follower over time, and cross-sectional studies, in which the observations are made on a single occasion. A third common option is the case-control design, in which the investigator compares a group of subjects who have a disease or condition with another group of subjects who do not.
Types of design:
Some of the most popular designs are sorted below, with the ones at the top being the most powerful at reducing observer-expectancy effect but also most expensive, and in some cases introducing ethical concerns.
The ones at the bottom are the most affordable and are frequently used earlier in the research cycle, to develop strong hypotheses worth testing with more expensive research approaches.
Experimental
Randomized clinical trial
Double-blind
Single-blind
Non-blind
Non-randomized clinical trial
Non-experimental
Cohort study
Prospective cohort
Retrospective cohort
Nested cohort
Case-cohort study
Case-control study (case series)
Nested case-control study
Cross-sectional study
Descriptive
Community survey
Descriptive studies- used to study variation in frequency by demographic characteristics, place & time
Analytic studies researcher has a pre-specified hypothesis
Experimental Studies are conducted under controlled conditions where researcher manipulates some measure
Observational studies do not involve intervention
Observe natural course of events where changes in one characteristic is studied in association with changes in other characteristics
Often necessary when unethical or infeasible to manipulate exposure
Will give more details about types of study design with examples later in talk after we discuss some issues to consider when selecting a study design

11. Analytic Studies We can use analytical studies to test hypotheses.
We want to know:
Whether there is an association between hypothesized exposure and disease,
How strong the association is,
What proportion of cases are due to exposure, and
Whether there is an increased risk of disease with increased exposure (a dose-response relationship).
Experimental or observational
A previous FOCUS issue explained how to use information to generate a hypothesis (or educated guess) about the cause of an outbreak. But just as suspicion is not enough to warrant a conviction in a courtroom, you need evidence to support your hypothesis. In science, we use analytic studies to test hypotheses.
This issue of FOCUS describes different types of study designs that can be used to test a hypothesis. Which one to choose is up to you….
In field epidemiology, we call the specific cause of an outbreak the “exposure.” We want to know whether there is an association between our hypothesized exposure and disease, how strong the association is, what proportion of cases are due to the exposure, and whether there is an increased risk of disease with increased exposure (also known as a dose-response relationship). These questions and others can be answered with the results of a well designed analytic study. Two commonly used types of analytic studies are the cohort study and the case-control study.

12. Quantitative designs
Observational: studies that do not involve any intervention.
Experimental: studies that entail manipulation of the study factor (exposure) and randomization of subjects to treatment (exposure) groups

13. Quantitative Designs Analytic Descriptive Experimental Observational
Cohort
Cross-sectional
Case-control
Other
Randomized
Clinical Trial
Non-randomized
Descriptive
Community Survey
A fundamental issue is whether to observe the events taking place in the study subjects in an observational study or to apply an intervention and examine its effects of these events in a clinical trial. Among observational studies, two of the most common designs are cohort studies, in which a group of subjects is follower over time, and cross-sectional studies, in which the observations are made on a single occasion. A third common option is the case-control design, in which the investigator compares a group of subjects who have a disease or condition with another group of subjects who do not.
Types of design:
Some of the most popular designs are sorted below, with the ones at the top being the most powerful at reducing observer-expectancy effect but also most expensive, and in some cases introducing ethical concerns.
The ones at the bottom are the most affordable and are frequently used earlier in the research cycle, to develop strong hypotheses worth testing with more expensive research approaches.
Experimental
Randomized clinical trial
Double-blind
Single-blind
Non-blind
Non-randomized clinical trial
Non-experimental
Cohort study
Prospective cohort
Retrospective cohort
Nested cohort
Case-cohort study
Case-control study (case series)
Nested case-control study
Cross-sectional study
Descriptive
Community survey
Descriptive studies- used to study variation in frequency by demographic characteristics, place & time
Analytic studies researcher has a pre-specified hypothesis
Experimental Studies are conducted under controlled conditions where researcher manipulates some measure
Observational studies do not involve intervention
Observe natural course of events where changes in one characteristic is studied in association with changes in other characteristics
Often necessary when unethical or infeasible to manipulate exposure
Will give more details about types of study design with examples later in talk after we discuss some issues to consider when selecting a study design

14. Experimental Design time outcome Intervention no outcome Study
RANDOMIZATION
Intervention
no outcome
Study
population
outcome
Control
no outcome
Experimental Design
baseline
future
time
Study begins here (baseline point)

15. Think more, Think Well, It Can be Easier!
One of the simplest experimental designs is the ONE GROUP PRETEST-POSTTEST DESIGN--EXAMPLE?
One way to examine Efficacy of a Drug:
O X O2
Measure DRUG Measure
Patients’ Condition Experimental Patients’ Condition
(Pretest) Condition/ (Posttest) intervention
RESULT: Significant Improvement from O1 to O2 (i.e., sig. O2 - O1 difference)
QUESTION: Did X (the drug) cause the improvement?

16. Research question 1:
Does perinatal exposure to TDF have any effect on bone development during the first 10 years of life?
Study design?
Research question 2:
Does the use of a particular vaginal microbicide ring during pregnancy have any effect(s) on birth outcomes?
Research question 3
Why is the up-take of contraceptive formulation X low in women ≤ 30 years of age

17. Questions or Comments ?
As we saw from the Aids-Floridation example, the above two are not enough.
We try to do it primarily through (statistical control and sample selection) to a lesser degree.